Colorado Naturalization records online and Colorado Citizenship Records online may include declarations of intent, petitions for naturalization, oaths of allegiance, certificates of citizenship, passports, and more.

These records often provide names and aliases of a person, age, country of birth, ethnic background, date and port of arrival, the name of the ship, previous residences, or current address.

You can look at federal (1870-1920) and state census (1825-1925) records to see if your ancestor was naturalized. See Colorado Census Records online for census record links and other helpful sources. Also see Colorado Emigration and Immigration Records online.

TIP – Login with your free FamilySearch account to unlock some collections — see other tips for opening FS resources.

KEY to collections

FS=FamilySearch FREE but login with your free account to access
Anc$=Ancestry – fee site
MH=MyHeritage – fee site
AG – AccessGenealogy
CSA – Colorado State Archives
CSS – Center of Southwest Studies at Fort Lewis College
DCL – Douglas County Libraries
FGS – Foothills Genelogical Society
GTHG – Genealogy Trails History Group
KMW – Karen Mitchell Websites
RW – RootsWeb
WCGS – Weld County Genealogical Society

Colorado Naturalization Records online at the federal level

US – Naturalization Records – United States, New England Petitions for Naturalization Index, 1791-1906, index & images, at FS

Colorado Naturalization Records online at the state level

Colorado – Naturalization Records – Colorado Naturalization Records, 1876-1990, index & images, at FS

Colorado – Naturalization Records – Colorado naturalization records, 1876-1990, at FS

Colorado – Naturalization Records – Naturalization records created by the U.S. District Courts in Colorado, 1877-1952 : NARA RG21 publication M1192, at FS

Colorado – Naturalization Records – Naturalization Records at CSA, at CSA

Colorado – Naturalization Records – Index to Naturalization and Declarations of Intent 1877-1929, at FGS

Colorado Naturalization Records online at the county level

Bent County – Naturalization and Citizenship – 1889-1903 Bent County naturalization index, at CSA

Clear Creek County – Naturalization and Citizenship – 1865-1867 Clear Creek County naturalization index, at CSA

Clear Creek County – Naturalization and Citizenship – 1878-1906 Clear Creek County naturalization index (not a definitive index for this time span), at CSA

Clear Creek County – Naturalizations – County Court Naturalizations, at FGS

Clear Creek County – Naturalizations – District Court Naturalizations, at FGS

Delta County – Naturalization and Citizenship – Journals (civil), 1899-1934, at FS

Delta County – Naturalization and Citizenship – Naturalization Records, V. 1-2, 1884-1906, at FS

Douglas County – Naturalization and Citizenship – Naturalization Records 1871-1896, at DCL

Huerfano County – Naturalization and Citizenship – Naturalizations 1882-1929, at HC

Huerfano County – Naturalization and Citizenship – Huerfano County Naturalization Records, at KMW

Larimer County – Naturalization and Citizenship – Naturalization Records ; Card Indexes, 1872-1958, Ca. 1872-1906, at FS

Larimer County – Naturalization and Citizenship – 1860-1958 Larimer County naturalization index, at CSA

Las Animas County – Naturalization and Citizenship – 1872-1915 Las Animas County naturalization index, at CSA

Park County – Naturalization and Citizenship – 1903-1906 Park County naturalization index, at CSA

Park County – Naturalization Records – County Court Naturalization Intentions Index 1881-1906, at FG

Park County – Naturalization Records – County Court Naturalization Records Index 1865-1941, at FG

Park County – Naturalization Records – County Court Naturalization Records Index 1880-1904, at FG

Park County – Naturalization Records – County Court Naturalization Records Index 1903-1906, at FG

Pitkin County – Naturalization Records – Pitkin County Naturalization Records 1888-1908, AA

San Juan County – Naturalization and Citizenship – Declarations of Intention ; Card Indexes, 1878-1942, 1877-1929, at FS

San Juan County – Naturalization and Citizenship – Final Naturalization Records, 1904, at FS

San Juan County – Naturalization and Citizenship – Naturalization Records, 1880-1906, at FS

San Juan County – Naturalization and Citizenship – Naturalization Records, Ca. 1882-1929, at FS

San Juan County – Naturalization and Citizenship – Naturalization Records, 1880-1906, at FS

Weld County – Pioneers – Weld County Master Index, at WCGS

Weld County – Naturalizations – Witnesses on Weld County Naturalization Index Cards, at WCGS

Colorado Naturalization Records online at the city level

Denver – Naturalization and Citizenship – Colorado Naturalization Records : COLLECTION RECORD, 1876-1990, at FS

Denver – Naturalization and Citizenship – Colorado Naturalization Records, 1876-1990, at FS

Denver – Naturalization and Citizenship – Naturalization Records Created by the U.S. District Courts in Colorado, 1877-1952 : NARA RG21 Publication M1192, at FS

Denver – Naturalization and Citizenship – Denver and Pueblo Naturalization Records Index, at DPL

Denver – Naturalization and Citizenship – Declarations of Intention 17 April 1877 to 3 December 1929, at FGS

Durango – Naturalization and Citizenship – Durango, CO naturalization records, at CSS

Colorado Naturalization Records online