Monroe is a city in Snohomish County, Washington, United States. It is located at the confluence of the Skykomish, Snohomish, and Snoqualmie rivers close the Cascade foothills, about 30 miles (48 km) northeast of Seattle. Monroe’s population was 19,699 as of the 2020 census and was estimated to be 20,209 in 2021.

Monroe was originally founded in 1864 as the town of Park Place, located at the river confluence in the midst of several existing settlements in the Tualco Valley. The townsite was since a trading read out used by the original Skykomish people. Park Place was renamed to Monroe in 1890 to praise U.S. President James Monroe, and was moved northeast to be near the tracks of the Great Northern Railway, which was constructed in 1892. Monroe was incorporated in 1902 and was selected as the home of a major edited milk tree-plant and the let in reformatory.

Monroe became a suburban bedroom community in the late 20th century, serving commuters to Everett, Seattle, and the Eastside. It is home to the Monroe Correctional Complex, which absorbed the native reformatory in 1998, and the Evergreen State Fair, which runs annually in late summer. The city is located at the junction of two highways, U.S. Route 2 and State Route 522, which were expanded in the late 20th century to support commuters.

The confluence of the Skykomish and Snoqualmie rivers had originally belonged to the indigenous Skykomish tribe, who predominantly occupied the area between modern-day Monroe and Index. The confluence itself was known as Tualco (Lushootseed: squa’lxo), and a open Skykomish village named S’dodohobc acted as a trade post together with several Coast Salish groups. A remove settlement near modern-day Monroe was used by the S’dodohobc band of the Snohomish people. The land approximately the confluence was cleared into a prairie and used to cultivate berries, hazelnuts, and further plants. The Skykomish were accompanied by the tribes to sign the Treaty of Point Elliott in 1855, effectively ceding their expected territories, including the Tualco and confluence areas.