St. Patrick's Day festivities are in full swing with the usual merriment, but political tensions linger in the Northeastern United States, where city leaders will be conspicuously absent from parades over gay rights issues.
New York City Mayor Bill De Blasio will become the first mayor in decades to sit out the traditional march because parade organisers refuse to let participants carry pro-gay signs.
Boston Mayor Martin Walsh wasn't marching in his city's parade either, after talks broke down that would have allowed a gay group to march.
Still, thousands of green-clad spectators came out for the parade in Boston, and a similar scene played out in downtown Philadelphia.
In Georgia, the dome of Savannah's City Hall will be lit green, and several thousand people braved icy temperatures to march with pipe and drum bands in Detroit and Bay City, Michigan.
In Ireland, St. Patrick's Day provides the launch of the country's annual push for tourism, a big part of the rural economy.
"To Irish people by birth or descent, wherever they may be in the world, and to those who simply consider themselves to be friends of Ireland, I wish each and every one of you a happy, peaceful and authentically Irish St. Patrick's Day," Irish President Michael D. Higgins, the ceremonial head of state and guest of honor at Monday's parade in Dublin, said in a statement.
Ireland's head of government, Enda Kenny, became the first Irish prime minister to attend Boston's annual St. Patrick's Day breakfast.
But Kenny has resisted pressure, in both Ireland and America, to support the gay rights lobby's demand to have equal rights to parade on St. Patrick's Day and he planned to march on Monday in New York (local time).
"The St. Patrick's Day parade [in New York] is a parade about our Irishness and not about sexuality, and I would be happy to participate in it," he said in Dublin before leaving for a six-day trip to the US.
Parade organizers have said gay groups are not prohibited from marching, but are not allowed to carry gay-friendly signs or identify themselves as LGBT.
Some LGBT groups plan to protest the parade along Manhattan's Fifth Avenue on Monday. Others will gather at the city's historically significant Stonewall Inn, where the gay rights movement was born, to dump Guinness beer from its shelves in protest of the beer company's parade sponsorship.
Other beer companies have joined the boycotts, with Sam Adams withdrawing its sponsorship of Boston's parade and Heineken following suit in New York.
New York's parade, a tradition that predates the city itself, draws more than 1 million spectators and about 200,000 participants every March 17. It has long been a mandatory stop on the city's political trail, and will include marching bands, traditional Irish dancers and thousands of uniformed city workers.
Several global landmarks will be bathed in green as part of a push by Ireland's tourism agency, among them Sleeping Beauty's Castle at Disneyland Paris in France, as well as the French capital's Moulin Rouge nightclub.
Other locations transforming at night under green floodlights are the Petrin Lookout Tower in Prague; Rhine Falls near Zurich; the Taj Mahal in India; the London Eye Ferris wheel; Niagara Falls; the Las Vegas welcome sign; New York City's Empire State Building; the Leaning Tower of Pisa; Sydney Opera House in Australia; and both the Giza pyramids and the Sphinx in Egypt.