Dow volunteered to serve in the Maine militia at the outbreak of the Civil War, but was blocked by his politically powerful father from fighting.

[3] In 1871, Dow began his political career with an appointment to the staff of Republican governor Sidney Perham.

He served as a delegate at large to the Republican National Convention at Chicago in 1880 which nominated James Garfield and Chester Arthur as its ticket.

As a result, Dow was appointed by now President Arthur to replace the recently deceased Lot M. Morrill as Collector of the Port of Portland, a highly prestigious and lucrative position.

Dow then turned his attention to building the Republican Party nationally through the creation of permanent social clubs.

Upon the election of Republican Benjamin Harrison to the presidency in 1888, Dow declined the post of Collector until his term as Speaker ended.