The lidded park to cover the open ditch of Interstate 5 that cut through downtown Seattle had been hotly debated throughout the process of planning the freeway in the late 1950s and early 1960s. Landscape architects and environmental advocates argued for the park's potential to mitigate the impact of the freeway's "ditch" design on downtown.
Highway engineers protested, citing high cost estimates and construction delays, as well as lack of available federal funding. Although 90 percent of the cost of constructing the Seattle Freeway (Interstate 5) came from federal coffers, that money could not be used on rerouting local arterials or on non-structural aesthetic mitigation projects like the proposed lid.
Freeway Park was not realized until 1976, when four-and-a-half acres of landscaping were completed on a newly built lid over the downtown part of Interstate 5 between Seneca and University streets. This project, funded with combined state, federal, and city funds, was a belated attempt to mitigate the impact of Interstate 5 on downtown Seattle.
Landscape architect Lawrence Halprin (1916-2009) designed Freeway Park.