This surge of construction was dubbed "Manhattanization" by opponents and led to local legislation that set some of the strictest building height limits and regulations in the country. In 1985, San Francisco adopted the Downtown Plan, which slowed development in the Financial District north of Market Street and directed it to the area South of Market around the Transbay Terminal. Over 250 historic buildings were protected from development and developers were required to set aside open space for new projects. To prevent excessive growth and smooth the boom-and-bust building cycle, the Plan included an annual limit of for new office development, although it grandfathered millions of square feet of proposals already in the development pipeline. In response, voters approved Proposition M in November 1986 that reduced the annual limit to until the grandfathered square footage was accounted for, which occurred in 1999.