According to the latest information available, the County Road K boat ramp in Jefferson, Wisconsin is a concrete ramp that measures approximately 14 feet wide. This boat ramp services the Rock River, which spans across several counties in Wisconsin, including Jefferson County.

The Rock River is a popular waterway for boating, fishing, and other recreational activities. The Wisconsin Department of Natural Resources (DNR) permits various types of watercraft on the Rock River, including motorized boats, sailboats, canoes, kayaks, and paddleboards.

It is important to note that regulations and restrictions may vary depending on the specific section of the river and the local ordinances in place. It is always recommended to check with the local authorities or the Wisconsin DNR for the most up-to-date information on permitted watercraft and regulations.