Route 104 is a short highway in Washington County, Missouri. It begins and ends at Route 21 in Washington State Park. No towns are along the route.

Route 104 begins at an intersection with Route 21 in Washington State Park, heading northeast as a two-lane undivided road. The route runs through forested areas of the state park, curving north before winding to the east. The road heads south before a turn to the northeast. Route 104 makes another curve to the south and ends at another intersection with Route 21.

The entire route is in Washington County.

Location	mi	km	Destinations	Notes
Washington State Park	0.000	0.000	Route 21
	1.379	2.219	Dugout Road
	3.206	5.160	Route 21
1.000 mi = 1.609 km; 1.000 km = 0.621 mi