There's an item at the Foster Hall Collection, University of Pittsburgh. Calvin Elliker (in Stephen Collins Foster: A Guide to Research, Garland, 1988, pp. 54-55) annotated it as follows:
Howard, John Tasker. Report on the Investigation to Determine Possible Connection Between Stephen C. Foster's 'Camptown Races' and Irvington, New Jersey (Formerly Known as Camptown): Aug.-Sept. 1935. 9p.
Commissioned by Josiah K. Lilly. Carried out in response to a claim made in the Cincinnati Gazette of January 2, 1857, which stated that the town of Camptown, New Jersey, had changed its name because of the association with Foster's Camptown races. The article claimed that whenever a citizen was asked where he or she lived and replied, "Camptown," the inquirer would involuntarily respond, "Do-dah, Do-dah!" Howard sates that he never believed there was any connection between the name of the song and the name of the town, as there had always been too small a black populaton to warrant a dialect song, and there was no evidence a racetrack had ever existed there. His findings concerning the reason for the change of name were inconclusive, but it did not appear that either Foster or his song were mentioned during the town meeting in which the change was approved. Irvington was named for Washington Irving, who thanked its citizens for the compliment, but declined their invitation to attend the re-naming ceremony. Apparently never published, as there is no OCLC record. The typescript in teh Foster Hall Collection may be unique.