This 2002 book explains how the 1785 Land Ordinance was implemented in a new system of surveying and sales of public lands. The surveying system was first used in Ohio and then used, with modifications, in the remainder of the Northwest Territory and other western U.S. territories. The book also explains each of the land reserves in Ohio (i.e. Western Reserve, Military Reserve etc.), as land distribution in each reserve varied from the standard system.
Knepper, George W., The Official Ohio Lands Book (pdf file: slow download)
As a typical example of how land holdings were measured and described prior to the system devised for the Northwest Territory, here’s a land sale transaction from Washington County, New York in 1836, in the FamilySearch Research Wiki database of County records. Read the first entry for “Indenture” on page 270 (image 463) of this Deeds book.
This Family Search Wiki is available for anyone to use free of charge, and has an enormous, but incomplete, collection of county court records online. It is great for genealogical research, but just as great for simply browsing.
In contrast to the New York example above, you can see here a land sales transaction in Ohio, using the new system. On the first screen, click the “Accession” number for any of the four land purchasers there, and then look at the “Patent Image” for the document that transferred land from the Federal Government’s land office to the buyer.
This database is from the Federal Bureau of Land Management’s “General Land Office” (GLO) records of public land sales. This site can be used for all the Great Lakes States and for many other states. Only the initial sale of a land parcel by the government is contained here, not subsequent sales. For records of these other transfers, try the FamilySearch site above to search county court records.
To carry out a search on the GLO database you will need the township number and range number, not the township name. To get these numbers, you can look through the late 19th century county atlases on the site Historic Map Works for the township, and look on the township map at the borders of the township for township and range numbers. You may have to check more than one county atlas.
For a full explanation of this numbering system, and much more, see the Official Ohio Lands Book at the top of this post.