Ft. Wilkins is not, in itself, worthy of a drive from St. Louis. It is nicely maintained, interesting, but so small that you can see all of it in under 2 hours.
However, there is much more on the Keweenaw Peninsula to see that would make the trip well worth it. There is:
A tour of the Franklin Copper Mine at Hancock
Keweenaw National Historic Park
The Jampot - A monastery that sells the best pastries and jams
Brockway Mountain Drive - scenic
Boat trip to Isle Royale National Park
And McLain SP for camping.
For more info, see: https://www.keweenaw.info/