A form of water transportation that was

popular in early Illinois

Steamboat

Explanation:

With various rivers surrounding the settlement and commerce in Illinois, such as the Mississippi, Ohio, and Wabash rivers together with Lake Michigan. Thus, with the Illinois River flows from near Chicago around St. Louis; the needs for steamboats as a means of water transportation that could navigate these waterways were determined.

Hence, by mid of 19th century, Peoria, the greatest of Illinois' inland river cities, has over 1200 steamboats, showing a great use of steamboats in the area.

Steamboats were considered to be the technical wonders of the age. This light-draft boats was developed by the 1830s and was known by its capability to carry "ten tons of freight on eight inches of water."