They formed the Eastlake Investment Company, in which Church owned two-thirds and Patten owned one-third of the company. Three reservoirs in Eastlake held water to irrigate land subdivided into plots of 80- and 160-acre farms. The Union Pacific Railroad was built by the fall of 1907 and daily service started on November 11, 1908. Farmers used rail to ship crops and livestock to market in Denver, and trains also took people to downtown. The town of Eastlake was officially platted by the Eastlake Investment Company on November 7, 1911.
The Eastlake State Bank opened in 1910, and both a dance hall and pool hall started operating.
A man named William Hopkins established a lumber operation, a general store, bank, and drugstore in town. Founder Andrew Patten owned a hotel boardinghouse, and Dr. R. D. Elmore cared for the sick in Eastlake. The Eastlake Post Office opened on June 8, 1912, and an Eastlake blacksmith shop operated in town. Around 1914, the Eastlake Grain Elevator opened, and the Farmers Co-Operative Elevator was built around 1920. That same year, Eastlake School opened for grades 1-12. The First Congregational Church of Eastlake was built around 1915, and Our Lady of Sorrows Catholic Church opened by 1917.
Eastlake was its own community for about 80 years before joining Thornton. In 1990, Eastlake residents voted for annexation by the City of Thornton to connect to city sewer service. The Eastlake Post Office still serves the 80614 Eastlake zip code, so Eastlake continues to truly retain an identity and charm all its own.