The 41st parallel was also one of the principal baselines used for surveying a portion of lands in Ohio. This marked the southern boundary of the Connecticut Western Reserve and the Firelands using the western boundary with Pennsylvania as the principal meridian. It also served as the baseline for a later survey of Ohio land north of the Greenville Treaty line up to the Fulton line which was the original boundary between Michigan and Ohio under the Northwest Ordinance (see the Toledo Strip). The later survey used the boundary with Indiana as the meridian.