IRAD Fact Sheet for Will County Compiled by Ted Cash. The below information was obtained from the Illinois State Archives

Established: January 12, 1836 (Laws, 1836, p. 262)
Present area, or parts of it, formerly included in:
1831–1836 Cook
1833–1836 Iroquois
1826–1836 Vermilion
1825–1827 Putnam
1823–1825 Edgar
1823–1825 Fulton
1819–1823 Clark
1821–1823 Pike
1816–1823 Crawford
1815–1816 Edwards
1812–1815 Madison
1801–1812 St. Clair
1790–1801 Knox, Northwest Territory
County Seat:
1836– Joliet—Name changed from Juliet on May 24, 1845.
History of county governing board:
1836–1850 County Commissioners’ Court
1850– County Board of Supervisors
Township Government
Adopted: November 6, 1849
Township Names:
Channahon
Crete
Custer Formed from Reed and Wilmington (date unknown).
DuPage
Florence Formed from Wilmington (date unknown).
Frankfort
Green Garden Formed from east half of Trenton (date unknown).
Homer
Jackson
Joliet
Lockport
Manhattan Formed from west half of Trenton (date unknown).
Monee Name changed from Carcy (date unknown).
New Lenox Name changed from Vernon on June 10, 1850.
Peotone Formed from east half of Wilton (date unknown).
Plainfield
Reed Name changed from Clinton on June 10, 1850.
Troy
Washington Formed from Crete and Sherburn (date unknown).
Wesley Formed from southeast part of Wilmington (date unknown).
Wheatland
Will Formed from Carcy (now Monee) and Sherburn (date unknown).
Wilmington
Wilton
Notes:
Bourbonnais, Momence and Rockville were townships established in 1850, but the area therein became part of Kankakee County when it was formed in 1853.
Sherburn and Trenton were townships established in 1850, but the area therein was absorbed into other townships. See above.