In 1863, he began studying law in Plattsburgh in the office of Judge Peter S. Palmer and Smith M. Weed.
[4] In 1867, Holcomb moved to New York City, where he was managing clerk in the office of corporation counsel John E. Delvin.
In 1875, he moved back to New York City and joined the law firm Matthew, Husted & Folly.
[1] He later became senior member of the law firm Holcomb, Martin & Weil, which had offices at 49-51 Chambers Street.
[5] In the Assembly, he was chairman of a special committee on enumeration and apportionment, which investigated the recent federal census in New York City.