Using a tax record to determine the movements of a family is only one of the many ways tax records can help with genealogical research. Quoting from the FamilySearch.org Research Wiki article on United States Taxation:
Governments have collected taxes in the United States since the colonial era. Tax records vary in content according to the purpose of the assessment. They may include the name and residence of the taxpayer, occupation, description of the real estate and name of the original purchaser, description of some personal property, number of males over 21, and the number of school children, slaves, and farm animals. Annual tax lists can help establish ages, residences, relationships, and the year an individual died or left the area. They can be used in the place of missing or destroyed land and census records.One advantage of searching for tax records is that they are maintained at every level of government. The challenge is that few of these records are readily available online and indexed. To begin a survey of the availability of tax records, it is useful to consult the FamilySearch.org Catalog. The FamilySearch Catalog is useful, not just to locate research material in the Family History Library, but also as a finding aid to learn what types of records may be available at different jurisdictional levels. For example, a search in the Catalog for "United States" returns an extensive list of sources including several relating to taxation. Here is a screenshot of that portion of the list showing the categories listed under taxation:
By clicking on the triangle arrow, the topic of Taxation (6) is expanded as follows:
At this point, the researcher may conclude that searching for tax records is too difficult and turn to other sources. But this list merely illustrates the point that tax records and not usually included in the types of records considered to be genealogically important. It also points out the fact that tax information may be mixed in with other records, such as my example of gleaning tax information from the Rhode Island Town Records.
I can illustrate the issue of availability by doing a search on the U.S. National Archives website for tax records.
You may not be able to read the results of this search, but there are 774 results returned for "tax records." In the case of one set of records, "Income Tax Records of the Civil War Years," the actual original records are in the National Archives in Boston, Massachusetts. However, this particular record set is digitized and available on Ancestry.com as "U.S. IRS Tax Assessment Lists, 1862-1918." By the way, this is not a source that normally comes up with a general search of Ancestry.com records. It is best searched directly by going to the Ancestry.com Card Catalog and looking for tax records.
Tax records are really "good news -- bad news" for genealogists. The good news, of course, is that this type of record may contain very valuable information. The bad news is that finding and gaining access to these records is more difficult than many other types of records.