The Root River system began forming about 20,000 years ago as Wisconsin’s glaciers retreated. Beginning in eastern New Berlin, it flows through southwest Milwaukee County and enters Lake Michigan at Racine. Rich in fish and game, the river and its drainage area attracted many Native Americans, with the Potawatomi remaining until their departure by treaty in the 1830s. In the area now within Greenfield, later residents found numerous stone artifacts, a copper tool from ca. 3000-500 BC, many small stone points, and a trove of projectile points uncovered by a boy during the 1950s. Later nineteenth- and early twentieth-century settlers struggled to farm there, and during the mid-twentieth century houses built on the floodplain were soon demolished after several floods. Charles Whitnall included Root River Parkway in his 1923 master plan for the Milwaukee County Parks System, and land acquisitions during the New Deal era led to its creation as a major recreational resource. Milwaukee County landscape architect Alfred Boerner designed the parkway and its units, including Boerner Botanical Gardens and Arboretum, which were built by laborers in the Civilian Conservation Corps, Works Progress Administration, and other Depression-era work programs. In 2013, portions of Root River Parkway were listed in the National Register of Historic Places.