Longview Lake is a 930-acre freshwater reservoir in parts of Kansas City, Lee's Summit, and Grandview, all in Jackson County, Missouri. The reservoir is part of Little Blue River Project for flood control, recreation, and fish and wildlife conservation. The lake is located in the 4,852-acre Longview Lake Park, which is managed by Jackson County Parks an…Longview Lake is a 930-acre freshwater reservoir in parts of Kansas City, Lee's Summit, and Grandview, all in Jackson County, Missouri. The reservoir is part of Little Blue River Project for flood control, recreation, and fish and wildlife conservation. The lake is located in the 4,852-acre Longview Lake Park, which is managed by Jackson County Parks and Recreation.