Here is more specific info on the park at Columbus.

Itch-Kep-Pe Park

Directions:

South of Columbus on Montana Highway 78. The city
(!population just over a thousand) of Columbus is north of
the Yellowstone River,
continue traveling south and right before crossing the
Yellowstone River, you will find Itch-Kep-Pe Park.v

Camp Sites: 30
Trailers: Yes
Toilets: Yes
(oh, good)
Water: Yes
Boat Launch: Yes
Fishing: Yes
Swimming: Yes
Stay Limit: 14 days

Season of Operation:
4/1-10/31

On the Montana Travel website, you will see the tourist bureau has divided the state into different regions they have named (for marketing purposes, of course). Billings is in "Custer Country" and Columbus is in "Yellowstone Country".