Eighty miles west of Bozeman, copper-mining BUTTE is bunched on a steep, almost treeless hillside where massive black headframes of long-abandoned pits soar up among paint-bare homes, stark gray business premises, and a ring of surface workings and dirty-yellow slag heaps. It's an oddly compelling landscape, best appreciated at dusk, when the golden pink light casts a glow on the mine-scoured hillsides, and the old neon signs illuminate uptown's historic brick buildings.

Exploration of this friendly, atmospheric town soon reveals a community rich in ethnic and trade union culture. Among immigrants to leave their mark were the Irish - Butte still hosts the biggest St Patrick's Day celebrations in the Rockies, with an estimated 40,000 customers passing through the famous old M&M Bar every March 17 - and miners from Cornwall ; the traditional meat-and-potato pasty ( PAST-ee) is still served in most cafés.

From its early days, Butte stood out as a "Gibraltar of Unionism" in the anti-union West. Miners used their collective strength to obtain a minimum wage and an eight-hour day, and it became impossible to get work without a union card. Such confidence bred radicalism, and Butte sent the largest delegation to the founding convention of the IWW (the "Wobblies") in 1906. The eventual consolidation of mining operations under the huge Anaconda Company led to inter-union rivalries and rioting, and in 1983 the last mine closed. Today conflicts rage between the clean-up lobby (the town's largest disused mine, the Berkeley Pit, is slowly filling with heavily poisoned groundwater) and the traditionalists, keen to develop new methods to exploit the mineral-rich seams that once made Butte the "richest hill on earth." To take a look at the ecological disaster that is the 700ft by mile-long Berkeley Pit , head for Continental Drive. Here, a viewing platform surveys the whole horrifying mess, the most toxic stretch of water in the United States (summer daily 8am-9pm; free).

Uptown lies Butte's extensive historic district . On W Park Street, the excellent, although rather grandly named, World Museum of Mining (daily 9am-6pm April-Oct; $4) is packed with fascinating memorabilia from the local boom years. Outside, beyond the scattered collection of rusting machinery - baffling to all but experts - its 35-building Hell Roarin' Gulch re-creates a cobbled-street mining camp, complete with saloon, bordello, church, schoolhouse and Chinese laundry. Above it all looms the blackened headframe of the 3200-foot-deep Orphan Girl mineshaft.

In an old noodle parlor at 17 W Mercury St, the tiny Mai Wah Museum (June-Aug Tues-Sat 11am-3pm; free) focuses on the history of Butte's Chinese community with its small, intriguing collection of photos, cooking implements, kites, fireworks, menus and books. At the end of the nineteenth century the narrow strip between Galena and Mercury streets was known as China Alley, the bustling heart of a 600-strong community; by the 1940s widespread racism had reduced the number to just a few families. At the other end of the cultural spectrum is the Dumas Brothel Museum , 45 E Mercury (May-Sept daily 9am-5pm; tours $3.50; tel 406/782-3808, ). The Dumas was built as a brothel in 1890 and stayed in business until 1982. It's the only surviving building in what was once a thriving red-light district, and the guided tour gives you a good insight into what life was like for the occupants and their clients during Butte's heyday. The tour takes in the building's underground "bedrooms," accessible through tunnels that connected with the uptown business district.

At night the 90ft Our Lady of the Rockies statue is illuminated by floodlights. Built entirely by voluntary labor - there had just been a major layoff at one of the mines - it was set in place on top of the Continental Divide, some 3500ft above Butte, by helicopter.