One of the largest tracts, the Connecticut Western Reserve, was a concession to the state of Connecticut for the sufferings of ill-fated towns in Connecticut during the Revolutionary War. The most famous tract in Ohio is the Virginia Military District. This region was reserved for the distribution of military bounty warrants by the state of Virginia. As well, the U.S. had a similar tract located in Ohio. Lands transacted between individuals are found on the county level, in the County Recorder's office.
Further reading is necessary for a better understanding of Ohio's land groupings and collections.
Smith, Clifford Neal. Federal Land Series. Peters, William E. Ohio Lands and Their Subdivisions. Hone, E. Wade. Land and Property Research in the United States.