It was created out of Tryon County in 1778. By studying the county divisions of North Carolina one learns that what eventually became Lincoln County was part of Anson County in 1760, which in turn was created in 1750 from Bladen County. The records the researcher needs will be in Colonial North Carolina sources and filed under Anson and Bladen counties. In many local histories you will find eulogies of families, often filled with errors, especially in respect to early generations of lines. However, local histories, published prior to 1885 are generally fairly accurate for the family history of the Revolutionary and post-Revolutionary periods, for they are based, for the most part on statements made by members of the family who had knowledge of the persons and events of the periods.
Most university libraries contain extensive collections of U.S., county and state histories.
Just because you are over 25 does not mean you can't go back to school and use the library. Of if you are going to Washington, D.C., area, then you'll want to stop at the Library of Congress. Many libraries have a copy of this valuable multi-volume reference set.