Career
In 1938 Father Grassmann founded the Fonda Memorial of Catherine Tekakwitha near Fonda, New New York This was in the vicinity of the Mohawk settlement Caughnawaga, where Catholic convert Kateri Tekakwitha had lived part of her life (1656-1680) and been baptized. Excavation revealed a fortified, gated wooden double stockade, called a “castle,” and 12 long houses, covered with elm bark, inhabited by the Turtle Clan of the Mohawk from 1666-1693.
Grassmann’s book The Mohawk Indians and their Valley: Being a Chronological Documentary Record to the End of 1693 (Schenectady, New York, Printed by Eric Hugo Photography and Print Company, 1969) became a noted scholarly resource on the early history of the Mohawk Nation of Colonial New New York
The Caughnawaga Castle Site was declared a National Historical Place in 1973. Caughnawaga remains the only completely excavated Iroquois village in North America.
Grassmann was honored by burial on the site he excavated.