The Katy Trail State Park is a state park and recreation area in St. Charles County, Missouri. It is a recreation rail trail that runs for 240 miles from Machens to Clinton in the state of Missouri.

Following the National Trails System Act of 1968 that allowed the conversion of railroads to trails, the Katy Trail State Park was created after the former Missouri-Kansas-Texas Railroad was closed to business after the Missouri River?s flooding repeatedly washed out the train tracks along the said route. Instead of repairing, the company decided to abandon the railway. This allowed the creation of the recreational trail that is now popular for hiking, biking, and horseback riding.

The Katy Trail State Park is open all year round.