The idea of green space for large, monumental sculpture in Seattle, was first discussed by Virginia and Bagley Wright, Mary and Jon Shirley (former president of Microsoft and Chairman of the Seattle Art Museum Board of Directors), and Seattle Art Museum director (and wife of William Gates Sr.) Mimi Gardner Gates.
  
The idea grew further during a discussion in 1996 between and Martha Wyckoff while stranded on a fly fishing trip in Mongolia due to a helicopter crash. Wyckoff, being a trustee of the Trust for Public Land, soon after began an effort to identify possible locations for the park. They settled with a land formerly used by Unocal (Union Oil of California) Corporation for storing, transferring, and shipping gasoline and diesel fuels, this 9-acre site required a massive toxic cleanup. A $30 million gift from Mary and Jon Shirley established them as foundational donors. Much of the sculpture comes from local collections or were specifically commissioned for the park.