An estimated 165,00 marchers paraded the 2-mile route along one of New York's main thoroughfares as bands and bagpipes blasted out a joyous musical beat starkly missing on the unusually quiet streets of Ireland's capital, Dublin, where a foot-and-mouth scare led officials to scrap the four-day carnival extravaganza.
New York's gray cityscape was punctuated by patches of vibrant green from green berets, scarves and lipstick and teens with dyed green hair among onlookers gathered six deep, to the Irish flags flapping in a brisk March wind.
The city's St. Patrick's Day parade is America's largest, followed by the version in the Southern city of Savannah, Georgia, where 35 bands and more than 50 floats wound their way around the historic City Market and River Street.
"It's been a blast," said one officer at the city police department, who estimated well over 200,000 people descended on downtown Savannah to watch the parade.
Savannah's love affair with St. Patrick's Day began in 1824 with its first unofficial parade, made up mostly of soldiers from various local regiments walking through town after celebrating Mass.
New York Mayor Rudolph Giuliani, wearing an emerald Yankees baseball cap, dubbed his city's parade "the beginning of spring," despite the gusty, chilly weather. Giuliani, a big booster of the annual Irish festivities, spent the day marching with the ranks of city firefighters and police officers.
Fifth Avenue's usual weekday growl of traffic was replaced by the cheerful beat of high school marching bands and plaintive tones of bagpipes, while young girls bedecked in green costumes danced Irish jigs where usually the only bright color is taxicab yellow.
In downtown Chicago, thousands gathered for the city's annual St. Patrick's Day parade that came complete with the traditional "greening" of a stretch of the Chicago River.
Even the river runs green in Chicago. A local plumbers union dyed the river the appropriate color as thousands of revelers braved the cold to watch a parade featuring 2,000 Irish dancers.
Marching bands, leprechauns and gaily decorated floats were among the attractions at the event that took place under mostly clear skies, as some labored to shovel snow dumped by a storm that swept through the city and suburbs on Friday.
And outside Boston, some of the celebrants are wagging their tails. The New England Irish Setter's Club is hosting a St. Patrick's Day party for dogs.
New York police reported that three female members of the Irish Lesbian and Gay Association were arrested along the parade route as they attempted to chain themselves to a fence to block he marchers in protest at organizers' refusal to allow gay groups to participate.
Two of the women were charged with disorderly conduct, and the third with assault for biting a police officer.