Denver is a borough in Lancaster County, Pennsylvania, United States. The population was 3,861 at the 2010 census, up from 3,332 at the 2000 census.
Denver was founded by Hans Bucher, a Swiss immigrant, in 1735. It was originally known as Bucher's Thal, or "Bucher Valley", in reference to the adjacent Cocalico Creek. In the mid-18th century, a gristmill was built along the creek ,and by 1772 six dwellings had been built. A blacksmith shop and a sawmill were operating by 1820. Early advantages for the settlement were fertile soils and the limestone formations that were mined for the manufacture of mortar, plaster and whitewash. In the 1830s, settler John Bucher became an advocate for using the lime as a fertilizer. Several limestone quarries were in turn operating by the 1850s.
During the Civil War, the Reading and Columbia Railroad built a line through town, prompting a name change to "Union Station". With time, residents grew weary being referred to as a train station.