According to the wiki on him Morgan, a lawyer he became a founding "warrior" of the Grand Order of the Iroquois. The fraternity of young white men adopted some of the social practices of the Iroquois, and were particularly interested in their confederacy. They dressed in traditional clothing and adapted some Iroquois rituals with the purpose of understanding the people better.
In 1844, Morgan moved to Rochester, New York, still within former Iroquois territory. He expanded his interests to learn more about Iroquois society. With the help of fellow "warriors," including Ely S. Parker, of Seneca descent, Morgan started to do pathbreaking ethnographic work: he studied facts to understand Iroquois society on its own terms. Inspired by Parker, Morgan and his fellow warriors worked to protect the Tonawanda Seneca reservation from being broken up by men eager for its land.
Read online Morgan's work Houses and House-Life of the American Aborigines