Exhibit 99.1

Contacts:

FOR IMMEDIATE RELEASE

AMEREN ANNOUNCES 2009 EARNINGS

ISSUES 2010 EARNINGS GUIDANCE

ST. LOUIS, MO., Feb. 18, 2010—Ameren Corporation (NYSE: AEE) today announced 2009 net income in accordance with generally accepted accounting principles (GAAP) of $612 million, or $2.78 per share, compared to 2008 GAAP net income of $605 million, or $2.88 per share. Excluding certain items in each year, Ameren recorded 2009 core (non-GAAP) net income of $615 million, or $2.79 per share, compared to 2008 core (non-GAAP) net income of $622 million, or $2.95 per share.

“I am pleased to report 2009 earnings per share in line with our expectations,” said Thomas R. Voss, president and chief executive officer of Ameren Corporation. “During 2009, we reduced planned spending, headcount and investment across the company to mitigate the negative impact on sales of a weak economy, the Noranda aluminum smelter outage and milder-than-normal weather.

“We also enhanced our financial strength and liquidity position by issuing new long-term debt and equity, extending our credit facilities and taking the difficult step of reducing our common dividend. Our regulated utilities are seeking rate increases to recover our costs and earn fair returns on investments. These actions have established a solid foundation for executing our future strategies and creating long-term shareholder value.

“Today we are also announcing 2010 GAAP and core earnings guidance of $2.20 to $2.60 per share,” Voss added. “The expected decline in 2010 earnings, compared to 2009, primarily reflects lower projected merchant generation segment margins.”

2009 Earnings Discussion

Core (non-GAAP) 2009 earnings per share declined, compared to 2008. Factors contributing to that decline included lower electricity and natural gas sales in the regulated utility businesses and lower margins in the merchant generation business — results of weak economic conditions, milder 2009 weather and, in our regulated Missouri utility, the Noranda aluminum smelter outage. Higher depreciation and interest expense and an increased average number of common shares outstanding

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also affected comparative results. Offsetting factors included new utility rates in Illinois and Missouri and lower operations and maintenance expenses due, in part, to the absence of a refueling outage at the Callaway nuclear plant.

At Ameren’s regulated utilities, milder weather and the economic slowdown led to a 3% decrease in kilowatthour sales to residential and commercial customers in 2009, compared to 2008. However, this sales decline was smaller, an estimated 1%, on a weather-normalized basis. The weak economy also led to a decline in kilowatthour sales by Ameren’s regulated utilities to their industrial customers. These sales declined 11% in 2009, compared to 2008, excluding the impact of reduced sales to AmerenUE’s largest customer, the Noranda Aluminum, Inc., smelter plant in New Madrid, Mo. Noranda’s plant sustained damage because of a power interruption on non-Ameren-owned power lines during a severe ice storm in January 2009. Electric sales to industrial customers, including Noranda, declined 17% in 2009, compared to 2008.

The following items were excluded from 2009 and 2008 core (non-GAAP) earnings, as applicable:

In the fourth quarter of 2009, Ameren recorded GAAP net income of $79 million, or 34 cents per share, compared to $57 million, or 27 cents per share, recorded in the fourth quarter of 2008. Excluding certain items in each period, Ameren recorded fourth quarter 2009 core (non-GAAP) net income of $85 million, or 37 cents per share, compared to fourth quarter 2008 core (non-GAAP) net income of $97 million, or 45 cents per share.

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A reconciliation of GAAP to core (non-GAAP) earnings per share is as follows:

2010 Earnings Guidance

Ameren expects 2010 GAAP and core earnings to be in the range of $2.20 to $2.60 per share. Any net unrealized mark-to-market gains or losses will impact GAAP earnings but are excluded from GAAP and core (non-GAAP) earnings guidance because the company is unable to reasonably estimate the impact of any such gains or losses at this time.

The projected decline in core earnings per share in 2010, compared to 2009, is primarily due to expected lower margins at Ameren’s merchant generation segment as a result of lower realized power prices, reflecting the economic slowdown, and higher fuel and related transportation costs, reflecting the expiration of lower-cost coal and rail contracts. The merchant generation segment has proactively sold forward or hedged approximately 90% of its expected 2010 generation output at an average price per megawatthour that is greater than the current market price; however, the 2010 average realized price is expected to be less than that of 2009. An increase in the average number of common shares outstanding, higher depreciation expense and a scheduled spring refueling and maintenance outage at the Callaway nuclear plant are among the other factors contributing to the expectation of lower earnings per share. The above factors are projected to be partially offset by, among other things, expected new electric and natural gas delivery rates in Illinois and new electric service rates in Missouri, effective in the second quarter of 2010; the expected return to service of the Taum Sauk pumped-storage hydroelectric facility; and the anticipated return to full operation of the Noranda aluminum smelter plant.

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Ameren expects its business segments to provide the following contributions to 2010 GAAP and core (non-GAAP) earnings per share:

Ameren’s earnings guidance for 2010 assumes normal weather for the year and is subject to, among other things, regulatory decisions and legislative actions, plant operations, energy and capital and credit market conditions, economic conditions, severe storms, unusual or otherwise unexpected gains or losses, and other risks and uncertainties outlined, or referred to, in the Forward-looking Statements section of this press release.

Missouri Regulated Segment Earnings

Core (non-GAAP) earnings in 2009 were $241 million versus $236 million in 2008. This earnings improvement was primarily a result of new electric rates, which took effect March 1, 2009, and lower operations and maintenance expenses due in part to the absence of a refueling outage at the Callaway nuclear plant in 2009. Callaway is refueled on an 18-month cycle. These positives were largely offset by reduced electric sales to native load customers due to milder summer weather, the weak economy and lower sales to the Noranda Aluminum smelter plant, as well as higher depreciation expense and financing costs, among other factors. Missouri regulated operations recorded GAAP earnings in 2009 of $259 million versus $234 million in 2008. In addition to those mentioned above, factors affecting the GAAP earnings comparison included a gain in 2009 as opposed to a loss in 2008 from net unrealized mark-to-market activity, expenses in 2009 for employee separations, and benefits in 2008 of a Missouri rate order directing the recording of regulatory assets for previously incurred costs related to the January 2007 severe ice storm and a 2007 FERC order.

Illinois Regulated Segment Earnings

Core (non-GAAP) earnings in 2009 were $127 million compared to $51 million in 2008. This earnings improvement was primarily due to new electric and natural gas delivery service rates that took effect Oct. 1, 2008 and lower operations and maintenance expenses. These positives were partially offset by lower electric and natural gas deliveries due to milder weather and the weak economy, as well as higher financing costs, among other factors. Illinois regulated operations recorded GAAP earnings in 2009 of $124 million versus $32 million in 2008. In addition to those mentioned above, factors impacting the GAAP earnings comparison were lower charges in 2009 related to the Illinois electric settlement agreement reached in 2007, a swing to a gain in 2009 from a

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loss in 2008 from net unrealized mark-to-market activity, expenses in 2009 for employee separations and the absence of 2008 asset impairment charges.

Merchant Generation Segment Earnings

Core (non-GAAP) earnings in 2009 were $273 million, a decline from $336 million earned in 2008. This decline was largely due to lower sales volumes and higher fuel and related transportation costs, as well as higher financing and depreciation expense. These negative factors were offset, in part, by higher realized power prices and lower plant operations and maintenance expense. Proactive forward sales and hedges of 2009 generation, executed in prior years at higher-than-2009 market prices, largely shielded merchant generation segment earnings from the impact of falling market prices for power. GAAP earnings from merchant generation operations in 2009 were $247 million, down from $352 million in 2008. In addition to the items noted above, the GAAP earnings comparison reflected lower charges in 2009 related to the Illinois electric settlement agreement reached in 2007, a loss in 2009 as opposed to a gain in 2008 from net unrealized mark-to-market activity, charges for employee separations in 2009 and asset impairments in 2008 and 2009 and the 2009 portion of the lump-sum settlement payment received and recorded in 2008 related to a terminated coal contract.

Analyst Conference Call

Ameren will conduct a conference call for financial analysts at 9:00 a.m. Central Time on Thursday, Feb. 18, to discuss 2009 earnings and other matters. Investors, the news media and the public may listen to a live Internet broadcast of the call at www.ameren.com by clicking on “Q4 2009 Ameren Corporation Earnings Conference Call,” followed by the appropriate audio link. An accompanying slide presentation will be available on Ameren’s Web site. This presentation will be posted in the “Investors” section of the Web site under “Webcasts and presentations.” The analyst call will also be available for replay on the Internet for one year. In addition, a telephone playback of the conference call will be available beginning at approximately noon Central Time, from Feb. 18 through Feb. 24, by dialing, U.S. (877) 660-6853 or international (201) 612-7415, and entering account number 352 and ID number 343213.

About Ameren

With assets of $24 billion, Ameren serves approximately 2.4 million electric customers and almost one million natural gas customers in a 64,000-square-mile area of Missouri and Illinois. Ameren owns a diverse mix of electric generating plants strategically located in its Midwest market with a generating capacity of more than 16,300 megawatts.

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Regulation G Statement

Ameren has presented certain information in this release on a diluted cents per share basis. These diluted per share amounts reflect certain factors that directly impact Ameren’s total earnings per share. The core (non-GAAP) earnings per share and core (non-GAAP) earnings per share guidance excludes one or more of the following: the earnings impact of the 2007 settlement agreement among parties in Illinois for comprehensive electric rate relief and customer assistance, net unrealized mark-to-market gains or losses, the costs of employee separations in 2009 and asset impairment charges in 2008 and 2009, a lump-sum payment in 2008 from a coal supplier for expected higher fuel costs in 2009 as a result of the termination of a contract, the benefit in 2008 of a rate order from the Missouri Public Service Commission directing the recording of regulatory assets for previously incurred costs for the January 2007 severe ice storm and a 2007 Federal Energy Regulatory Commission order. Ameren uses core (non-GAAP) earnings internally for financial planning and for analysis of performance. Ameren also uses core (non-GAAP) earnings as primary performance measurements when communicating with analysts and investors regarding our earnings results and outlook, as the company believes it allows it to more accurately compare the company’s ongoing performance across periods.

In providing consolidated and segment core (non-GAAP) earnings guidance, there could be differences between core (non-GAAP) earnings and earnings prepared in accordance with GAAP for certain items, such as those listed above. Ameren is unable to estimate the impact, if any, on future GAAP earnings of such items.

Forward-looking Statements

Statements in this release not based on historical facts are considered “forward-looking” and, accordingly, involve risks and uncertainties that could cause actual results to differ materially from those discussed. Although such forward-looking statements have been made in good faith and are based on reasonable assumptions, there is no assurance that the expected results will be achieved. These statements include (without limitation) statements as to future expectations, beliefs, plans, strategies, objectives, events, conditions, and financial performance. In connection with the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, we are providing this cautionary statement to identify important factors that could cause actual results to differ materially from those anticipated. The following factors, in addition to those discussed elsewhere in this release and in our filings with the Securities and Exchange Commission, could cause actual results to differ materially from management expectations suggested in such forward-looking statements:

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Given these uncertainties, undue reliance should not be placed on these forward-looking statements. Except to the extent required by the federal securities laws, we undertake no obligation to update or revise publicly any forward-looking statements to reflect new information or future events.

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AMEREN CORPORATION (AEE)

CONSOLIDATED OPERATING STATISTICS

AMEREN CORPORATION (AEE)

CONSOLIDATED OPERATING STATISTICS

AMEREN CORPORATION (AEE)

CONSOLIDATED STATEMENT OF INCOME

(Unaudited, in millions, except per share amounts)

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CONSOLIDATED BALANCE SHEET

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CONSOLIDATED STATEMENT OF CASH FLOWS

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