National Archives microfilm publication M1285 serves as an index to some naturalizations from 1840-1950 for the counties listed below. The 1840-1950 time frame varies by county. For Chicago and Cook County, Illinois, this index begins in 1871. The Cook County naturalization records prior to that were destroyed in the Chicago fire.
Ancestry has digitized the index cards from this National Archives microfilm publication and included them in this database:
U.S. Naturalization Record Indexes, 1791-1992 (Indexed in World Archives Project) (at Ancestry/requires payment) includes searchable digitized naturalization index cards from NARA Publication M1285
FamilySearch also has a database for this index:
Illinois, Northern District Naturalization Index, 1840-1950 (at FamilySearch/free)
This microfilm publication uses the Soundex system for indexing surnames. What does Soundex mean?
- National Archives Microfilm Publication M1285. Title: Soundex Index to Naturalization Petitions for the United States District and Circuit Courts, Northern District of Illinois, and Immigration and Naturalization Service District 9, 1840-1950 (179 rolls). This serves both as an index to naturalization petitions from the two Federal courts mentioned in its title and as an index to naturalization petitions filed in county courts in eastern Iowa, northwestern Indiana, eastern Wisconsin, and northern Illinois. Specifically, the following counties are included:
- Illinois counties: Boone, Bureau, Carroll, Champaign, Cook (includes Chicago), DeKalb, DuPage, Ford, Fulton, Grundy, Henderson, Henry, Iroquois, Jo Daviess, Kane, Kankakee, Kendall, Knox, Lake, LaSalle, Lee, Livingston, Marshall, McHenry, McLean, Mercer, Ogle, Peoria, Putnam, Rock Island, Stark, Stephenson, Tazewell, Vermilion, Warren, Whiteside, Will, Winnebago, and Woodford.
- Indiana counties: Benton, Fulton, Jasper, Lake, LaPorte, Marshall, Newton, Porter, Pulaski, St. Joseph and Starks.
- Iowa counties: Allamakee, Appanoose, Benton, Black Hawk, Bremer, Buchanan, Butler, Cedar, Chickasaw, Clayton, Clinton, Davis, Delaware, Des Moines, Dubuque, Fayette, Floyd, Grundy, Hardin, Henry, Howard, Iowa, Jackson, Jefferson, Johnson, Jones, Keokuk, Lee, Linn, Louisa, Mahaska, Mitchell, Monroe, Muscatine, Scott, Tama, Van Burean, Wapello, Washington and Winneshiek.
- Wisconsin counties: Adams, Brown, Calumet, Columbia, Crawford, Dane, Dodge, Door, Florence, Fond du Lac, Forest, Grant, Green, Green Lake, Iowa, Jefferson, Kenosha, Kewaunee, Lafayette, Langlade, Manitowoc, Marinette, Marquette, Menominee, Milwaukee, Oconto, Outagamie, Ozaukee, Portage, Racine, Richland, Rock, Sauk, Shawano, Sheboygan, Walworth, Washington, Waukesha, Waupaca, Waushara, Winnebago and Wood.
This publication is also available at the LDS Family History Library in Salt Lake City. Click on the link below for more information and microfilm roll numbers...
Microfilm Information: Soundex Index to Naturalization Petitions for U.S. District & Circuit Courts, Northern District of Illinois and INS District 9, 1840-1950 (at the FHL) (look for the camera icon next to the microfilm roll numbers for digitized copies of the microfilm rolls)
Finding US Naturalization Records - A Genealogy Guide
Online Illinois Naturalization Records
Chicago Genealogy Records and Sources on the Internet