Investigative Case Files of the Bureau of Investigation 1908-1922 (located on Fold3.com) are not just about anti-American activities during the time period around World War I. While many of the files do center around German natives living in the United States, there are materials on other individuals and other types of actions.
This screen shot comes from an investigation in Columbus, New Mexico into Jack Demoss and Mary White. Demoss was accused of acquiring and selling whiskey and Mary White (his housekeeper) was accused of running a bawdy house. There is a fair amount of testimony in the file. Demoss indicates other locations he had lived before this incident and a location of a previous arrest is given.
These images are available on Fold3.com.
Many other files are investigations into draft evasion, the occasional house of ill repute near a military base, etc. The draft evasion files usually contain some proof of age and the house of ill repute cases, well they contain information as well.
Do not just assume that these files are only about Germans. That would be a mistake.