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This map focuses on the irrigation infrastructure surrounding the St. Vrain Creek in portions of Larimer, Boulder, and Weld Counties, Colorado. It showcases the network of ditches, reservoirs, and irrigated lands that supported agriculture in this semi-arid region.

The towns of Lyons and Longmont are prominent, reflecting the area's dependence on irrigation for settlement and farming. The map also illustrates the distribution of irrigated parcels and the interconnected water systems vital to regional agricultural development.  It also includes the names of dozens of landowners.

Irrigation History of Larimer, Boulder, and Weld Counties:

The South Platte River, including St. Vrain Creek and other tributaries played a central role in the development of irrigation in northern Colorado, beginning in the 1870s. Early settlers in the region recognized the necessity of harnessing the creek's flow to transform the arid plains into productive farmland. Boulder County saw the establishment of several irrigation projects, with settlers constructing the Left Hand Ditch and other smaller canals by the early 1870s. These projects served to irrigate farmland near Longmont and Lyons, enabling the growth of crops in previously dry areas.

Larimer County’s role in irrigation revolved primarily around its western areas bordering the St. Vrain Creek system. Smaller ditches, fed by tributaries of the creek, supported farms in the foothills near Lyons. Although less extensive than Boulder County's projects, Larimer's irrigation efforts expanded as settlements grew, and by the late 19th century, the infrastructure had developed into a reliable system for farming operations in the area.

Weld County benefited greatly from water diverted from the St. Vrain Creek through ditches and canals that irrigated large expanses of farmland. By the late 19th century, projects such as the Highland Ditch and other smaller irrigation systems made it possible to cultivate the county’s flat, fertile lands. Weld County quickly became one of the most productive agricultural regions in Colorado, relying on the dependable flow of St. Vrain Creek to sustain crops like alfalfa, sugar beets, and wheat.

The creation of reservoirs along the St. Vrain Creek was critical to these irrigation efforts. These reservoirs provided storage during periods of low flow, ensuring a consistent water supply for agriculture. By the early 20th century, the collaborative management of irrigation systems in these counties had led to a thriving agricultural economy in the region, transforming the landscape and securing water resources for generations of farmers.

This map encapsulates the ingenuity and determination of settlers who utilized the St. Vrain Creek to overcome the challenges of farming in an arid climate, leaving a lasting legacy of irrigation infrastructure that continues to shape the region today.