This is an interesting story from St. Louis Magazine. How many have you done? One thing I did not know about but plan to do in the near future is climb to the top of the Compton Hill Water Tower which is number 4 on the list.
"The city from the top of the water tower, one of seven such towers remaining in the country. This one’s elegant French Romanesque, built in 1898 to costume a 100-foot standpipe, and a haunt of architects for its 360-degree view of the city." At Grand near 44.
I've climbed to the roof of Luther Tower on the seminary campus many times and the view is fantastic, but it sure would be fun to go up into an 1800's tower.