Bureau of Land Management - General Land Office Records - Online access to Federal land conveyance records for Colorado and other Public Land States, including image access to more than 5 million Federal land title records issued between 1820 and the present. Survey plats and field notes dating back to 1810.
Colorado Historic Newspaper Collection - Searchable online database includes more than 500,000 digitized pages, representing 163 individual newspaper titles published in Colorado from 1859 to 1923.
Colorado State Archives - Collection includes historical records and information generated by state and local governments in Colorado including military, prison, school, mining, and railroad records.
Family Search - Free family history, family tree, and genealogy records and resources provided by The Church of Jesus Christ of Latter-Day Saints.
Ancestry.com - Subscription service provides access to over 7 billion genealogy records including federal census records, birth, death & marriage records, immigration, and military records.
Stephen H. Hart Research Center - Provides access to the collections of History Colorado, including books, maps, architectural drawings, private and business correspondence, family albums, photographic prints, magazines, and newspapers.
Building Technology Heritage Library - Page through digital copies of rare architectural trade catalogs, house plan books, and technical building guides from the 1800s through 1963. A great resource for historical design details and construction practices.