Horace Augustus Hildreth was born in Gardiner, Maine, the son of an attorney. Hildreth attended local schools before graduating from Bowdoin College in the class of 1925 and receiving his LL.B. from Harvard University in 1928.

Gardiner is a city in Kennebec County, Maine, United States. The population was 5,961 at the 2020 census. Popular with tourists, Gardiner is noted for its culture and old architecture. Gardiner is a nationally accredited Main Street America community. It is included in the Augusta, Maine micropolitan New England City and Town Area.