Located in the Big Belt Mountains near Helena but far enough away to feel quite remote (then again, this is Montana, where just about everything feels remote outside posted city limits), Avalanche Gulch has a great deal of limestone sport climbing for people of all ability levels. Although a handful of trad routes exist, as is typical of limestone areas, most of the climbing is sport.
The Mountain Project page for Avalanche Gulch currently lists sixteen crags. Some of those crag pages have route pages attached, and some have none while mentioning that there are bolted routes there. I am not aware if there is a guidebook covering the area, which has other limestone sport areas such as Hellgate Gulch. Because I have spent just one day at two crags here (Nude Beach and Nude Beach SW Face), I am not claiming this SP page is a definitive source for the location, but I am hoping users will find it and the link to the MP page helpful.
For now, this will stand as a mountain/rock page with some specific directions for the Nude Beach crags, but if it gets any development via crag pages, I will turn it into an area/range page.
Nude Beach crags: On MP, these three crags have almost as many route pages as the other thirteen do, and they are easy to locate. After you cross into the national forest and enter the canyon, you will reach a cattle guard and culvert. Park at a pullout here or close by and walk up the road a short distance (a few minutes). The buttress with the Nude Beach crags is on the left and almost touches the road. An easy-to-locate climbers trail heads up from the road, and pictures here should help with locating the buttress as well.
Nude Beach proper (5.4-5.10b) is the farthest from the road but only takes a few minutes to reach. Then there is Nude Beach Cove (5.7-5.10a), followed by Nude Beach SW Face (closest to the road, 5.8-5.10d). Routes at Nude Beach SW begin up on a prominent ledge.
A nice feature (in my opinion) at Nude Beach and perhaps elsewhere in Avalanche Gulch is that most routes have small tags at the first bolts identifying the name, grade, and person who developed the route.
The two nearest cities/towns are Helena and Townsend.
From Helena, take Canyon Ferry Road east past the dam and the north end of the lake and then head south. Turn left onto Avalanche Gulch Road. Plan on about an hour.
From Townsend, get onto U.S. 12, go left on 284, and bear right (north) at a major split. Then turn right onto Avalanche Gulch Road. Give yourself about an hour.
All year, but summer is best. It's Montana.
No developed campgrounds, but there are dispersed spots. There are lots of campgrounds along the lake not too far away.