City of O'Neill
Residents in O'Neill prepare for the St. Patrick's Day celebration in March honoring the patron saint of Ireland. The celebrations have doubled the population of the "Irish Capital of Nebraska" each year for the past several years.
O'Neill, which was founded by an Irish native and proclaimed the "Irish Capital of Nebraska" by the governor in 1969, is home to the world's largest shamrock.
City officials began by painting the giant shape at the intersection of Highways 20 and 281 in the middle of town, but decided to make it permanent in concrete in 1993. (You can even see its outline on Google Maps.)
These days, the giant shamrock is a big tourist attraction, with people coming all year to see it. There have even been proposals and weddings at the site, Fritz said.
On St. Patrick's Day, the city of about 4,000 doubles its population, with visitors flocking to see the painting of the shamrock (it gets a fresh coat of paint every year just before the main celebrations), O'Neill's grand parade, Green Eggs and Ham -- a children's breakfast that features green scrambled eggs -- and other activities.
(parts taken from CNN article - 2011)