Counties with significant record loss are referred to as 'burned counties' by genealogists. Burned counties are a setback to researchers, but do not always present an insurmountable problem. Alternate sources exist for 'burned counties', such as copies of tax records kept by state auditors, superior court appeal records, manuscript collections, private abstract companies, records of surrounding counties, and others. When you encounter county record loss crucial to your research, think of it as a learning experience, an opportunity to become a creative genealogist. Your searches in county records will be aided by your understanding of both the court system and the land record survey system used in your area of interest.
Court systems differ from state to state and from one time period to another.
A land survey system is the method used to divide land into identifiable parcels so it can be described in deed records. Two of the most common land survey systems are the rectangular survey system and the metes and bounds system. Paul Wallace Gates has written, History of the Public Land Law Development , a very detailed book about the development of the United States land system and his book should be available to you in your local library or through interlibrary loan. To learn about the rectangular system, read Subdivisions of the Public Lands by J.S. Higgins, a reprint of an 1894 textbook on the subject. Briefly, the rectangular system is used from the Midwest through the western states and involves a grid of numbered ranges and townships superimposed on the landscape.