Complex sentence: On July 8,1788, Phelps met with the five nations of the Iroquois Confederacy (including Mohawks, Oneidas, Onandagas, Cayugas, and Senecas) at Buffalo Creek to execute a deed or treaty for rights to a portion of their land.
Split into simpler sentences: On July 8,1788, Phelps met with the five nations of the Iroquois Confederacy, including the Mohawk, Oneida, Onandaga, Cayuga, and Seneca nations, at Buffalo Creek. His goal was to execute a deed or treaty and obtain title to a portion of their land.