There are at least 11 Keithley families that can be identified, living in Harford, Cecil, and Talbot counties.
Two of these families, those of Francis Keithley (c. 1730), and a Keithley of unknown first name (c. 1650),
have been documented somewhat. By the middle-to-late 18th century, family connections can be proved. It is
likely that some of these families are related, and that there are really only about three separate families.
All of these people are English.
View brief overview of the Maryland families (PDF)
Although these early Maryland families have not been well documented, the most knowledgeable resource for them is Frank Deis at Rutgers University. He may be retired by now.