In 1984, voters in San Francisco passed Proposition K, which prevents construction of any building over 40 feet (12.2 m) that casts a shadow on a public park, unless the Planning Commission decides the shadow is insignificant. This proposition causes problems for a proposed 75-story building south of Market Street, which would cast a shadow on a public park ten blocks away, for one hour of the day in the fall, as well as St. Mary's Square, Justin Herman Plaza, and Union Square for significant parts of the year. Massachusetts has similar laws against the casting of shadows on Boston Common, the Public Garden, and other important public open spaces.