[4] The city is the most densely populated municipality in northern New England, an area comprising the states of Maine, New Hampshire, and Vermont.

According to the United States Census Bureau, the city has a total area of 1.5 square miles (3.9 km2), of which 0.1 sq mi (0.2 km2) (5.30%) is covered by water.

As early as 750 CE, the Abenaki tribe lived along the shores of a cascading waterfall in a fertile river valley they called Winoskitegw, meaning “land of the wild onion".

Fort Frederick was never used for defense, but its presence increased the value of Onion River property and promoted settlement.

[7] After the Revolutionary War, Ira Allen built a dam across the river with a sawmill at each end.

The American Woolen Company purchased the failing Burlington Mills in 1901, restoring a measure of economic growth to the area.

[9] This success eventually led Winooski to incorporate as a city in 1922, breaking away from the town of Colchester.

[7] In the 1980s, two old mills were converted into commercial, office, and apartment space, helping to revitalize the area.

[10] Though the dome was never built, in 2009 the city's planner defended the concept, insisting, "Economically, it's a slam dunk," and adding, "You could have had year-round fly-fishing.