These limits, combined with the early 1990s recession, led to a significant slowdown of skyscraper construction during the late 1980s and 1990s. To guide new development, the city passed several neighborhood plans, such as the Rincon Hill Plan in 2005 and Transit Center District Plan in 2012, which allow taller skyscrapers in certain specific locations in the South of Market area. Since the early 2000s, the city has been undergoing another building boom, with numerous buildings over 400 feet (122 m) proposed, approved, or under construction; some, such as the two-towered One Rincon Hill and mixed-use 181 Fremont, have been completed. Multiple skyscrapers have been constructed near the new Transbay Transit Center, including Salesforce Tower, which topped-out in 2017 at a height of . This building is the first supertall skyscraper in San Francisco and among the tallest in the United States.