'Frederick Rohrer immigrated to America on the ship Restauration in 1747 as part of the larger Mennonite migration from Germany. Only Frederick and son Samuel were included on the ship list, but presumably Samuel's younger brothers Martin and John, and his sister Margaret who had married Michael Funk were there as well. Samuel bought his very first Washington County property named Funk's Run from Michael Funk in 1758. Michael was also on the Restauration.
Frederick Rohrer and his brother Jacob (1703-1758) owned land in Hagerstown just east of town in the bend of Antietam Creek. Rohrer's Mill (now called Trovinger's Mill) and the nearby old house was where they lived. Frederick's sons Martin and John owned land in that vicinity too, but his son Samuel bought property near Rohrersville in 1762, starting the Rohrersville branch of the family. Frederick's brother Jacob had a son Jacob (1748-1822) who ended up accumulating a lot of land east of Hagerstown, all the way to Chewsville and south to Rt. 40.'
Information from the data contributed by Michael W. Rohrer to the USGenWeb Archives Mar 8, 2003.
http://files.usgwarchives.net/md/washington/wills/rohrer-s.txt
The history of Rohrersville and the genealogy for the Rohrer line in MD is inconclusive. There seem to be two Frederick Rhorers in the area at that time, and it is unclear whether this Frederick is the correct ancestor, or whether the line should connect to Hans Michael Rohrer m. Katerina Schwagler. I believe the Frederick listed here is more likely.