Bechtel's business activities began in 1898 when cattle farmer Warren A. Bechtel moved from Peabody, Kansas, to the Oklahoma Territory to construct railroads with his own team of mules. Bechtel moved his family frequently between construction sites around the western United States for the next several years, eventually moving to Oakland, California in 1904, where he worked as the superintendent on the Western Pacific Railroad. In 1906, W. A. Bechtel won his first subcontract to build part of the Oroville-to-Oakland section of the Western Pacific Railroad. That same year, he bought his own steam shovel, becoming a pioneer of the new technology. He painted "W.A. Bechtel Co." on the side of the steam shovel, effectively establishing Bechtel as a company, though it was not yet incorporated.
Bechtel completed work on a series of railroad contracts during the early 1900s, culminating in an extension of the Northwestern Pacific Railroad finished in 1914.
Starting with the construction of Klamath River Highway in California in 1919, Bechtel ventured into jobs outside of building railroads. The company built roads, bridges, and highways throughout the western United States. The company worked on its first hydroelectric projects in the 1920s for Pacific Gas and Electric Company in California.
By the time Bechtel incorporated in 1925, it was the leading construction company in the western United States. In 1929, Warren's son, Stephen, urged his father to take on the company's first pipeline project. Bechtel began working with California Standard Oil Company to build pipelines and refineries.
In January 1931, Bechtel joined other contractors in the west to form Six Companies, Inc., a consortium created to bid for a contract from the US government to construct the Hoover Dam. Six Companies won the bid in March and construction on the dam began in the summer of 1931.