Raised as a Quaker, Letchworth learned the values of hard work, charity, and development of the intellect from his family.

"In 1875, he had inspected all the orphan asylums, poor-houses, city alms houses, and juvenile reformatories in the state which had an aggregate population of 17,791 children."

Letchworth spent the next few years traveling around Europe and the United States at his own expense to explore the treatment and condition of the insane, epileptics and poor children.

[3] Letchworth hired noted landscape architect William Webster to design the grounds of the estate, and named it Glen Iris.

In 1906, he bequeathed his 1,000-acre (4 km2) estate to New York state with the provision that the American Scenic and Historic Preservation Society serve as custodian of the land and allowing himself a life tenancy.