The 1855 population census for Illinois was compiled in each county by census commissioners appointed by the county commissioners courts and filed with the Secretary of State. The census was authorized under an 1845 act, as amended in 1855 (Rev. Stat. 1845, p. 89; L. 1855, p. 151). Each county return includes name of county and frequently names or legal descriptions of legal subdivisions contained in county (e.g., townships, cities, villages). Under each of these categories entries for each household include name of head of household, numbers of free white males and females in each decennial age group (e.g., ages 0-9, 10-19, 20-29), numbers of male and female Negroes and mulattoes, total number of inhabitants in household, number of males eligible for duty in state militia, type (e.g., mill, tinshop, saddleshop) and valuations of products of manufacturing establishments, valuations of livestock and products of coal mines, pounds of wool produced, and infrequent remarks (e.g., occupation of head of household, legal description of area covered by return). Also included in each return are numbers of colleges and common schools and numbers of pupils enrolled in each. Each return also includes signature of census commissioner certifying return, date certified, and frequent recapitulations of totals. Returns are included for the following counties:

Adams

Alexander

Bond

Boone

Brown

Bureau

Calhoun

Cass

Christian

Clark

Clay

Clinton

Coles

Cook

Crawford

Cumberland

De Kalb

De Witt

Du Page

Edgar

Edwards

Effingham

Fayette

Fulton

Greene

Grundy

Hamilton

Hancock

Hardin

Henderson

Iroquois

Jackson

Jasper

Jersey

Jo Daviess

Johnson

Kane

Kankakee

Kendall

Knox

La Salle

Lawrence

Lee

Livingston

Logan

McDonough

McHenry

McLean

Macon

Macoupin

Madison

Marion

Marshall

Mason

Massac

Menard

Mercer

Monroe

Montgomery

Morgan

Moultrie

Ogle

Peoria

Perry

Piatt

Pike

Pope

Pulaski

Putnam

Randolph

Richland

Rock Island

St. Clair

Saline

Sangamon

Schuyler

Scott

Shelby

Stephenson

Tazewell

Union

Vermilion

Wabash

Warren

Washington

Wayne

White

Whiteside

Williamson

Winnebago

A summary account which lists no individual names is also included for Champaign County.

Returns for Greene, Grundy, McLean, Macoupin, Richland, Sangamon, and Whiteside Counties also included censuses of deaf and dumb, blind, and insane persons conducted concurrently with the regular population census in each county as instructed by an 1855 House and Senate joint resolution (L. 1855, p. 741).  See CENSUS OF DEAF AND DUMB, BLIND, AND INSANE, RS 103.009.

Secretary of State, "State Census," Record Series 103.008, Illinois State Archives.