Security & related concerns among the citizenry led to the cancellation of these shows in late August. Advanced ticket sales had already been underway, with ca. 4,000 ducats sold.
GD would end up at Boston Music Hall for these dates ... not a bad landing, though presumably much, much smaller.
Red Wildy, "SPAC Postponing the Grateful Dead," Schenectady Gazette, August 30, 1972, p. 14 (accessed via Google News).
"2 Grateful Dead Concerts Canceled on Security Issue," New York Times, August 31, 1972, p. 27.