In 1851, Maine passed a law prohibiting the sale of alcohol, except for medicinal purposes. This is hard to picture in the Maine I know, land of 10,000 bars and home of Fat Ass in a Glass, a mixture of Allen's coffee brandy and milk.
Even at the time, the law did not go over well among Portland's large Irish population, They viewed it as an attack; Dow, a Quaker, devoted teetotaler and Abolitionist, saw the law as a social good, as much of the rum sold in the US at the time fueled the slave trade.
Dow was not just opposed to imported liquor, though: he conducted raids on groggeries and drinking establishments right in the Munjoy Hill neighborhood of Portland. When a rumor spread that the mayor was storing rum in vaults under City Hall, the Irish immigrant population were enraged by what they saw as his hypocrisy. (The Mayor had authorized the purchase for medicinal purposes, but had not appointed a committee to do the authorizing, so was technically in violation of the law.)
At that time a judge could grant a search warrant if any three citizens requested it. Such a request was made to search City Hall, and a judge granted it. With warrant in hand, the men were nevertheless denied entry.
An angry crowd formed as men got off of work. They threw bricks and rocks, and Dow called out the militia with orders to shoot. One man, John Robbins of Deer Isle, broke and unlocked the door to the store of liquor. He was immediately shot by the militia. The crowd dispersed but the militia continued to fire, and more people were injured.
Dow was later tried and acquitted on charges that he improperly obtained alcohol. He lost his re-election bid handily and never again held public office, though he ran for governor and then for president.