In 1817, the northern portion of the Ohio-Indiana border was surveyed and became known as the First Principal Meridian for lands surveyed in the northwest part of Ohio. Lands were surveyed into townships which were subdivided into sections. The 41st parallel north latitude became the base line. North townships were extended from the 41st parallel to the southern border of the territory governed by the Michigan Meridian. Ranges were counted east of the meridian until they meet the western border of the Firelands; there are no westward ranges in this survey. The sections in each township were numbered as per the Land Act of 1796. Two military reserves ceded in the Treaty of Greenville of twelve miles square, and two miles square had previously been surveyed, and were not included in the lands North and East of the First Principal Meridian. This tract includes all or part of the modern day Ohio counties of Paulding, Defiance, Williams, Fulton, Henry, Putnam, Hancock, Wood, Lucas, Ottawa, Sandusky, Seneca, and Erie.
