Monroe is a city in Snohomish County, Washington, United States. The population was 17,304 at the 2010 census.
The history of Monroe is intertwined with that of the Great Northern Railway which pushed over the Cascade Range at Stevens Pass and worked its way down the Skykomish River Valley.The new development was originally known as Tye City, but became Monroe when Park Place's main store, the one containing the U.S. Post Office, relocated and took up the name "Monroe at Park Place" in honor of James Monroe, the nation's fifth president. Because the U.S. Postal Department would not allow any new post offices to use double names, the post office, and eventually the town, became known simply as "Monroe."