Early bicycling advocate Harold "Zip" Morgan first conceived and laid out a 64-mile (103 km) trail in 1939.

The route made its way around the edge of the county and through natural resource corridors found along the rivers and lakefront.

[2] In September 2018, to improve wayfinding, sections of the trail were assigned colors and branch line names.

Scenery along the Oak Leaf Trail varies from woodland parks, nature reserves, and a wildlife corridor along the lakefront, to urban industrial settings in Milwaukee's downtown area.

[1] Following the Kinnickinnic River for most of its length, it turns north at each end to connect to the Milwaukee Art Museum in the east and Hart Park in the west.

The line was established in 1988 as the 76 East-West Trail, spanning 14.3 miles (23.0 km) and following much of the same route as it does today.

In 2015, a 3.1-mile (5.0 km) gap in the line between Hampton Avenue and Mill Road was filled atop a former Union Pacific right-of-way.

The line was established in 1967 as a 3.1-mile (5.0 km) bicycle-only pilot trail that started at McKinley Park, traveled north to Lake Park, made a loop, and traveled south until ending near the North Point Water Tower.

[1] It branches from the Root River Line to provide a loop route through Whitnall Park.