All Katy Trail trailheads are right on the trail - can't miss it. Use this link for a list of
all Katy Trail trailheads, actually all trail parking lots, which are mainly trailheads.
The only trail in Columbia that connects to the Katy Trail, to my knowledge, is the MKT Fitness Trail, which is about 9 miles long. This
regional map shows how the two trails connect. Sorry, I don't have a more detailed map at this time.