I have four combination guns by Illinois makers. Two are side-by-side and two are over & under. The side-by sides include one by John Schurr, Henry, Illinois, dating from the 1870's, and the other is stamped Henry Sears & Co., Rockford, Ill. Henry Sears was primarily a hardware & cutlery dealer. It is hard to say who actually made the gun, but it does not appear to be an import.
The over & under combination guns are: one by J. H. Green, Momence, Illinois; and one by Benjamin H. Walker, Galesburg, Illinois. The B. H. Walker started life as a swivel breech, but at some point early in its life, had a second lock added and the swivel locked up solid. I would imagine that the swivel became loose, and the owner took it to the nearest gunsmith and had the alteration done.
There were others in Illinois who made combination guns of both types, as well as swivel breech guns. Edward Kline, at Henry, Illinois, made three-barreled combination guns, and I have seen several. These had back action locks for the upper two barrels (usually both smoothbore), and used the trigger guard as a mainspring for an underhammer mechanism, which fired the rifle barrel beneath. Kline's guns normally have just one trigger that will fire whichever hammer is cocked, or all of them that are cocked, if that is your pleasure. He likewise made three-barreled rifles and three barreled shotguns, according to what a customer might want. He also made side-by-side double combination guns. John Schurr, who made the one that I have, worked for Kline until Kline left Henry, in the early 1870's. Kline was making combination guns in Henry during the 1850's, and usually mentioned them in his advertisements.