A 2001 walking tour of Main Street in Portland by Doris Sherrow (which I can no longer find online) lists the house at 576 Main Street as the home of Dr. Charles H. Gilbert with a construction date of 1856. It also explains that Gilbert married one of the daughters of Rev. Hervey Talcott, who lived next door at 572 Main Street. According to genealogical sites, it was Charles Henry Gilbert‘s father, Dr. Gershom Clark Hyde Gilbert (1817-1889) who married Rev. Talcott’s third daughter, Harriette in 1845. Dr. Talcott left Portland in 1867, later living for periods in Waterbury, Hartford and Westbrook.
Dr. Charles H. Gilbert House (1856)