21st Ave Boat Ramp offers a single-lane concrete launch with a small dock for accessing Castle Rock Lake and the Wisconsin River.

The facility features dirt parking and is located on a small dirt road that may have access issues during spring or after heavy rains.

The ramp provides public access to approximately 3,000 acres of woodland open to the public, with opportunities for boating, hiking, ATVing, snowmobiling, and horseback riding in the surrounding area.