Monitor is a small unincorporated community in Chelan County, Washington, United States. It is situated along the Wenatchee River about 8 miles upstream from its junction with the Columbia River in the fertile Wenatchee Valley.Monitor is part of the Wenatchee–East Wenatchee Metropolitan Statistical Area.The USPS ZIP Code for Monitor is 98836. According to data from the 2000 census, the total population in the Monitor ZIP code was 342 persons. Monitor itself is not incorporated, and is not tracked by the Census.Before the existence of Monitor, the area was known by settlers as Brown's Flat, named after Reuben Brown who settled there in 1885. In these days, the Wenatchee River formed the boundary between old Kittitas and Okanogan counties. At the site of Monitor a school was built to serve school districts on both sides of the river.