When Newport News was chartered as an independent city in 1896, Post was chosen to serve as acting mayor until the city's first municipal elections could be held. On July 1 of that year, he was elected. Post chose to serve only one term as mayor, stepping down in 1898.
In 1902 Post commissioned a handsome Beaux Arts style mansion on Huntington Avenue in the North End Neighborhood of Newport News. The Post house still stands, surrounded by its original wrought-iron fence at 5600 Huntington Avenue, the largest lot in the North End.
In 1911, he assumed the presidency of Newport News Shipbuilding & Dry Dock Company. He would hold that office until his death in 1912. The newspapers of the day attributed his death to "overwork", and heart failure.[2] His entire time in Newport News was spent serving as a kind of lieutenant for Huntington, who essentially built the city of Newport News to serve his railroad.[citation needed]