I did the Katy Trail Last year from St Charles to Clinton. The trail is paved with pack llimestone and is a lot like concrete in most places especially when it is dry. Many bicyclist have ridden it on narrow road tires but I don't advise doing it as there are a few places that are soft and the narrow tires will not work well then or in the case it rains a lot also. If you do ride it on road tires just be sure they are flat resistance and as wide as possible. A cyclecross tire would probably be better.

If you do ride it for about forty mile this will carry you in Daniel Boone Country where he lived the last years of his life. If you are into history this is interesting to see.

When I did it I was on my mountain bike with All Terain tires. When I do it again I will switch tires on my mountain bike to smaller tire with smoother tread, the opposite of what I would do for my road bike.