Mark from Lee's Summit on 11/30/2022 9:35:06 PM:
I would recommend that you take the St. Louis Metrolink light rail to Downtown St. Louis and start your Katy Trail adventure on the paved trails along the Mississippi River from the Arch. Depending on your flight arrival time, you can either stay at a hotel near the airport or in Downtown St. Louis.
From Downtown St. Louis and the Arch, you can take the paved Mississippi River Trail north about 15 miles, cross the Mississippi River into Illinois using the bike/ped only Chain of Rocks/Route 66 bridge, ride the paved Illinois levee trail (called the Madison County Confluence River Trail) north about 15 more miles to Alton, take the paved bike shoulder across Hwy. 67 Mississippi River bridge back into Missouri, and then use low traffic streets through West Alton to Machens. Through West Alton, the trick is use the two lane Hwy. 94 as little as possible, just look at Google Maps and you can see how you can use Saale Road and Dwiggins Road to parallel Route 94 almost all the way to Machens Road. I would then ride from Machens to St. Charles and enjoy yourself in old Downtown St. Charles right by the Katy Trail.
If you don't want to make it a Katy Trail roundtrip, then there are other options like taking the Rock Island Trail spur off of the Katy Trail into Kansas City.