The St. Mary NPS campground now has 4 showers located in the C loop, around site C-148. It looks like they renovated one of the old bathroom houses in C loop and added on a new building with the showers. You get one token per person per campsite per day from the entry station. Hours are 7:30 AM - 8:30 PM, you get 5 minutes. The two showers on the outside of the building are water saving showers that shut off after about 30 or 45 seconds until you push the button to restart them again. The 2 on the inside of the building are traditional shower heads. It's nice not to have to drive to Many Glacier or Rising Sun for a shower if you're staying in St. Mary. I haven't seen it mentioned on the board, so I thought I'd post.
Nick