HistoryGeo.com — An authoritative database of over 12 million General Land Office patents — the legal and conclusive evidence of title to land — that can be easily mapped. This site is fee based, but the investment is worth every penny.
Boulder County property deeds – The searchable database of recorded public documents dating back to the 1860s. Click the “login as Guest” button to get access from the county’s website. Saving or printing documents comes with a $2.25 fee. This fee is waived if you do your searching, file saving and document printing at the Boulder County Clerk’s office at 1750 33rd Street, Suite 200 in Boulder.
Latinos of Boulder County, Colorado, 1900-1980 (PDF) by Marjorie McIntosh. A free version of a terrific book documenting Eastern Boulder County’s Latino community.
Colorado Historic Newspapers Collection — A valuable research tool encompassing tens of thousands of pages of historical newspapers, including the Louisville Times editions dating from 1942 to 2014.
General Land Office records — Searchable database of land patents, section and township survey maps and surveyor field notes. Most of the GLO surveys for Boulder County occurred in 1864. When searching for a land patent using a person’s name, be sure to try variations of spelling, since some of the patents were misrecorded or mistranscribed.