The EPA is taking a final action finding that 37 states, the District of Columbia, and the U.S. Virgin Islands have failed to submit for EPA review and approval State Implementation Plans (SIPs) for improving visibility in the nation's national parks and wilderness areas. Under the Clean Air Act (CAA) and EPA's implementing regulations, states were required to submit these SIPs to EPA by December 17, 2007. These SIPs must contain a number of elements, including importantly: For each mandatory Class I federal area in a state, reasonable progress goals providing for an improvement in visibility for the most impaired days and ensuring no degradation in visibility for the least impaired days; a long-term strategy for improving visibility, including enforceable emissions limitations, for meeting the reasonable progress goals; and Best Available Retrofit Technology (BART) determinations for certain older existing stationary sources. By this action, the EPA is making a finding of failure to submit for those states that have not submitted a SIP or have submitted a SIP that addresses only part of the requirements.