The William G. Milliken State Park and Harbor (formerly named Tri-Centennial State Park and Harbor) is a public recreation area located on the Detroit River just east of downtown Detroit, Michigan, on a portion of the city's International Riverfront.

The state park's 31 acres (13 ha) include wetlands, paved trails, and a 52-slip harbor of refuge.

[3] A 63-foot (19 m) conical brick lighthouse tower, designed as a scaled-down replica of the Tawas Point Light, marks the harbor entrance.

[5] The William G. Milliken State Park's official address is 1900 Atwater Street, on the near east side of Detroit and adjacent to the Jefferson Avenue corridor.

[6] The park offers shoreline fishing, a picnic area with sail-covered pavilions, and a 52-slip harbor with transient and seasonal tie-ups.