As I have been mentioning all along, determining specific facts about our ancestors can take considerable effort. Researching back about 200 years or so in the United States involved readily available records such as U.S. Federal Census records but when you are trying to determine the details of a specific event in an ancestor's life, you must begin to use records that are less available and may or may not even exist.
Throughout the United States, highly personal historical records have been accumulated by state and local historical societies and colleges and universities. If you have finally identified an ancestor who lived during the American Revolutionary War Era from 1775 to approximately 1786 and was of the age that participation in the War was possible, then you need to start the process of locating pertinent records. You need to be aware that any type of record could be the key to connecting your ancestor with the War effort and these records could be found nearly anywhere records are stored or kept.
Let me give a hypothetical example. Let's suppose you are searching for an ancestor that lived in Georgia. This is not an area that you might immediately associate with the Revolutionary War. However, all of the 13 original colonies participated in the war effort and provided soldiers and other types of support. Once you have records indicating your ancestor's location, you need to broaden your search. There are 28 institutions of higher learning in the State of Georgia. One of these institutions, the University of Georgia, has three special collections libraries: The Hargrett Rare Book and Manuscript Library, the Richard B. Russell Library for Political Research and Studies, and the Walter J. Brown Media Archives and Peabody Awards Collection. If you take the time to search these libraries, you will find that The Hargrett Rare Book and Manuscript Library has specific collections of documents pertaining to the Revolutionary War in Georgia including rare maps. One researcher, I am acquainted with, found a Revolutionary War connection in this collection.
You just have to assume that the records are there and continue to search. If you think that everything is online and that simple searches in the large online genealogy programs are enough, you are mistaken.
You can find a list of the colleges and universities in each state by doing a Google search for the lists. Here is an example of the Wikipedia article on the colleges and universities in Georgia.
If your ancestor came from Georgia, the documents you are seeking making the connection to the Revolutionary War could be in any of the libraries of these institutions and you should probably extend your search to adjoining states. For comparison, you might take a look at the number of colleges and universities in North Carolina.
Extending my example of places to look in Georgia, the Georgia Genealogical Society has a list of genealogical and historical societies in Georgia. It also has a list of libraries and other resources for genealogical research. The point here is that every state has similar resources and information about your ancestor might be found in any of the listed institutions. I know I am repeating myself, but this seems to be a point that bears repeating since it is so commonly ignored.
Focusing on local and state records is important, but it is also important to look to national level collections. The New England Historic Genealogical Society has a large library and extensive online collections. The list of possible repositories can seem to be endless but the results from searching can be rewarding.
Here are the previous posts on this topic.