The construction of Hoover Dam not only meant that the Colorado River could be used for irrigation and electricty, it also meant that the largest man-made lake in the world would form behind it. The creation of Lake Mead, while providing the first National Recreation Area in the United States, unfortunately flooded Mormon settlements as well as countless Native American archaeological sites. In 1865 Mormon leader Brigham Young sent a group of pioneers to the Virgin River/Muddy River Valley. Territorial lines were not clearly established at the time, and the settlers believed that the valley they settled was in Utah, not Nevada as it was later determined. In 1871, when Nevada began demanding back taxes from the settlers, most families in the area headed for Utah. Until 1880, the only family in St. Thomas was that of Daniel Bonelli. Eventually, people migrated back into the area to farm the land and raise their families. In 1912 St. Thomas had become a stop for the railroad. A mix between agriculture and mining (salt and copper), the economy of St. Thomas provided the basis for a small but flourishing community.
Originally established as a religious settlement, the community life at St. Thomas revolved around the church and its activities. Many residents were members of community organizations, such as the Relief Society. Most days, however, were filled with chores of farm life. Orchards and vineyards were a primary agriculture focus. True pioneers, every person was responsible for providing an aspect of their family's livelihood. From milking a cow to building a house, all family members contributed. Everyone looked forward to dances, fairs, and church activities. Since many residents were related to each other, everything seemed to be a family event.
St. Thomas had already welcomed progress in the form of the railroad. Unfortunately, the next stage of progress in the Southwest would mean the end of the little town and surrounding communities. The construction of Hoover Dam would lead to a huge lake covering their homes. The surrounding towns of St. Thomas and Kaolin would be completely submerged.
As work on the dam progressed, the government began buying land throughout the towns in anticipation of the dam's completion. Some families had their houses moved to nearby towns that wouldn't be buried by the water. Others simply loaded their cars or wagons to make a fresh start. By June 1938 the bottled waters of the Colorado finally headed into the valley. In Memoirs of Matilda Reber Frehner, compiled by her children and grandchildren, Vivian Frehner recalled the move from St. Thomas:
When Dad and Mom and me got into the car I never saw her cry so hard in my life. She was shook up really bad. Also, it was quite a thing when they went to the Relief Society the last time. The old ladies got down there and it was just like a funeral. They did nothing but divide up things and cry.