His interest in the family history is what likely led him to organize the Underhill Society of America in 1892.

In early meetings of the Society, David Harris Underhill often presided and shared his research with other family members.

[5] He married Caroline Fidelia Green of South Starksboro, Vermont, on July 29, 1873, in Chappaqua, New York.

[3] A sizable collection of material on Underhill history and genealogy was accumulated and maintained in his home until his death in 1936.

The Underhill Society of America presently has offices and their archives in the basement of the Matinecock Masonic Lodge on West Main Street in Oyster Bay, New York, where many materials from the original David Harris Underhill collection are available to review.