Butte was driven to life by the rich mineral resources that lay underground. Gold and silver mining brought the city's population of forty men and five women in 1866 to 14,000 by 1885. However, it was Butte's copper, critical to the electrification of America, which gave Butte a 41 percent share of the world copper market and a population of 40,000 by 1910. The city's mineral wealth drew innovative mining technology, capital from the likes of Hearst and Rockefeller, and at least five railroad lines to exploit the resource. Paramount to the development of Butte's wealth, however, was the need for workers who came to Butte from more than 60 nations and ethnic groups. They worked hard, and often gave their lives to mining, making a significant contribution to the labor history of this country in the process. Severe winters and high temperatures underground required that miners build their homes near the mines, in the shadow of the tall gallows or head frames, contributing to a unique landscape of industrial, residential and commercial buildings. Butte, built on a hillside amidst its own industrial lifeblood, played a critical role in the development of our growing nation.