Lewis and Clark Caverns has a long and storied history since its discovery by local ranchers in 1882. It was first explored in 1898 using ropes extending down a long, vertical shaft and breaking through some formations — it was likely never entered by humans before. Private developers offered tours and battled with the Northern Pacific Railroad, who had been granted the land by the U.S. government. It was established as a national monument in 1908. It was disbanded as a national monument on August 24, 1937, and become the first state park in Montana in 1938. The Civilian Conservation Corps built a visitor center and made the cave open for tours by creating two new entrances and building a trail.
Today, the park is a popular place to visit, offering a lovely campground, hiking trails and tours of the cave from May through September. While it is not a pristine cave, it is well-preserved and does not have a lot of visible vandalism. The limestone formations are beautiful and varied. The trail is a bit strenuous but not difficult, with subdued lighting. There are three options for tours. The basic tour ($12 for adults and $5 for children) is two hours and involves a hike of about 2 miles. It includes a moderate climb and 600 steps. There is a shorter tour of just the lowest room accessible via a paved path (also $12 for adults and $5 for children). There is a wild cave tour ($30) using headlamps and candlelight in December.
The basic tour involves a 0.75-mile hike up a trail with a moderate grade and nice views of the surrounding area. Inside the cave the trail winds down over 600 steps through narrow and low passages and along steep drop-offs. There are handrails in all of the steep areas. The route is challenging enough to be fun, but it is not dangerous.