St Thomas was established near the confluence of the Muddy and Virgin Rivers in the 1860s and eventually became a well known stop-over between LA and Salt Lake City.
While the Hoover Dam was being built, the government purchased the entire town and relocated all the residents, including the cemetery. As Lake Mead filled, the town was abandoned and eventually covered by up to 60 ft of water. The recent decline in Lake Mead's level has re-exposed the town, and you can now wander among the remains.
If you go, be sure to download the nice pdf about the site from Lake Mead's website - there are none available at the trail head.
Check out the Triplog.
This hike is listed as One-Way.
When hiking several trails on a single "hike", log it with a generic name that describes the hike. Then link the trails traveled, check out the example.