There are some hotels close by along the Ohio River with large parking lots. There might be somewhere near those.
The town isn't very busy in my experience. Depending on the size of your RV you may be able to temporarily occupy a few spots and just park horizontally, If I brought my RV I would try to park around the superman statue and avoid the street side parking. The museum isn't very large, so you shouldn't take too long to need to worry about parking funny for a bit.
There are no parking areas immediately around the building, but there may be somewhere close by. It's in the "downtown" area so space is limited.
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