Exhibit 99.1

PXP

Plains Exploration & Production Company

IMPORTANT NOTICE REGARDING EXTENSION OF BLACKOUT PERIOD

AND RESTRICTIONS ON YOUR RIGHTS

TO TRADE PXP COMMON STOCK

Date: May 24, 2013

On April 18, 2013, we sent you a notice pursuant to Section 306(a) of Sarbanes-Oxley Act of 2002 and Regulation BTR promulgated under the Securities Exchange Act of 1934, as amended (“Regulation BTR”), to notify you of a trading restriction that is currently imposed on executive officers and directors of PXP because of a blackout period (the “Blackout Period”) applicable to PXP’s common stock (the “PXP Stock Fund”) under the Plains Exploration & Production Company 401(k) Plan (the “401(k) Plan”). The Blackout Period began on May 10, 2013 and was originally expected to end during the week of May 26, 2013. However, because the anticipated closing for the Merger (as defined below) is now later than originally anticipated, the Blackout Period is currently expected to end during the week of June 2, 2013. We will notify you via email if there are any additional changes that affect the dates of the Blackout Period. In addition, for current information on the timing of the Blackout Period, you may call Nora S. Knowles at (713) 579-6047.

As described in our notice dated April 18, 2013, during the Blackout Period, 401(k) Plan participants are unable to direct or diversify investments pertaining to, or obtain loans or distributions with respect to, their individual 401(k) Plan account balances that are invested in the PXP Stock Fund. The Blackout Period is necessary to enable the trustee of the 401(k) Plan to process 401(k) Plan participants’ elections with respect to shares of PXP common stock held through their individual account balances that are invested in the PXP Stock Fund in connection with the pending merger of PXP with and into Freeport McMoRan Oil & Gas LLC, a wholly owned subsidiary of Freeport-McMoRan Copper & Gold Inc. (the “Merger”). As a result of the Blackout Period, Regulation BTR requires that we impose trading restrictions on our executive officers and directors during the Blackout Period and that we timely notify our executive officers and directors, as well as the Securities and Exchange Commission, of the Blackout Period and subsequent changes in the beginning or ending dates of the Blackout Period.

During the Blackout Period, subject to certain exceptions, you are prohibited from directly or indirectly purchasing, selling or otherwise acquiring or transferring any shares of PXP common stock or other equity securities of PXP that you acquired in connection with your service or employment as a director or executive officer of PXP, including pursuant to options to acquire shares of PXP common stock and other derivative securities denominated in shares of PXP common stock or other equity securities of PXP. These restrictions apply regardless of whether you participate in the 401(k) Plan. Note that although conversions of PXP common stock or other equity securities of PXP into shares of FCX common stock in connection with the Merger, including your election of Merger consideration, are exempt from these trading restrictions, any shares of FCX common stock you acquire pursuant to such conversions may not be sold or otherwise transferred prior to the end of the Blackout Period.

Although shares of PXP common stock and other equity securities of PXP acquired other than in connection with your service as an executive officer or director of PXP are generally not covered by this prohibition, if you hold both covered shares or equity securities and non-covered shares or equity securities, any shares or equity securities that you sell will be presumed to come first from the covered shares and equity securities unless you can establish that the shares or equity securities were acquired from another source. Transactions covered by these restrictions are not limited to those involving your direct ownership, but include any transactions in which you may have a pecuniary interest (e.g., transactions by members of your family who share your household, as well as by certain entities in which you have

financial involvement). Given the complexity of these rules, you are urged to avoid any discretionary change in your beneficial ownership of PXP securities or derivatives or FCX securities or derivatives during the Blackout Period. Even if you think an exception applies to you, we ask that you not trade any PXP security or derivative or any FCX security or derivative during the Blackout Period unless you have advance written permission from PXP’s General Counsel.

If you engage in a transaction that violates these restrictions, you may be required to disgorge any profits realized from such transaction and you could be subject to civil and criminal penalties. Please note that the trading restrictions implemented due to the Blackout Period are in addition to, and not in lieu of, the trading restrictions imposed by PXP’s insider trading guidelines.

If you have any questions concerning this notice, the extension of the Blackout Period or the transactions affected by the Blackout Period, please contact Nora S. Knowles by telephone at (713) 579-6047 or by mail at 700 Milam, Suite 3100, Houston, Texas 77002.

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