This note by John Tasker Howard may be of help:

"Camptown Races was copyrighted and first issued by the Baltimore publisher, F.D. Benteen, February 19, 1850. Within a few years the town of Camptown, New Jersey, changed its name to Irvington. A newspaper writer suggested that Foster's race-track song had brought the New Jersey town so much notoriety that its citizens changed the name of their town in self-defense. Careful research into the Irvington records and into minutes of town meetings has unfortunately failed to verify the tradition." (A Treasury of Stephen Foster, Random House, 1949, p. 63)

~Masato