The organization of the township occurred April 2, 1850, at the house of Richard Fuller. Of the meeting held that day, Ezra Alger was chosen Moderator, and William Emmerson, Clerk. The election held that day resulted in the choice of the following officers: Supervisor, M. L. Dunlap; Clerk, Richard W. Everett; Assessor, William Emmerson; Collector, Samuel Hammel; Overseer of the Poor, Richard W. Everett; Commissioners of Highways, Thomas Croghan, Ezra Alger and John G. Frye; Justices of the Peace, James M. Pennoyer and William Dunlap; Constables, Samuel Hummel and Edward B. Stanley. The organization of the town was effected under the name of Monroe, but afterward, as there was another town of that name, the name Leyden was selected.
Originally the township was for the most part prairie, the exception being a strip of timber averaging about a mile in width extending from north to south along both sides of the Des Plaines River, but mainly on the east side of the river. The largest trees in this timber were white oak, and were about two feet in diameter.
In addition to the unincorporated areas, the following towns lie, whole or in part, within the Leyden Township borders: Rosemont (south of Devon Ave), Schiller Park, Franklin Park, Northlake (north of North Ave), River Grove, Elmwood Park, Melrose Park (north of North Ave), Park Ridge (south of Devon Ave), Norridge (most western part) and Bensenville (east of County Line Rd).