The United States' largest St. Patrick's Day parades are unfolding. While the St. Patrick's Day holiday is March 17, many major events are happening on Saturday this year. That often happens when the holiday lands on a Sunday. Manhattan's St. Patrick’s Day Parade dates to 1762 and is one of the world’s largest Irish heritage festivities. Crowds also are expected in Savannah, Georgia, where a humble St. Patrick’s parade held in 1824 has grown to become the South's largest. In Chicago, plumbers will once again turn the Chicago River green. They use a powder that organizers say is not harmful to the environment.
