In many countries, people traditionally wore their best clothes to their church on Sunday. Easter Sunday was considered to be one of the most important Sundays of the year, so people often bought new clothes for Easter which they wore to church. After the church services, people went for a walk around the town. This is thought to have led to the American custom of Easter parades.
One of the largest Easter parades is on Fifth Avenue in Manhattan in New York City. History.com tells us
the Easter Parade tradition dates back to the mid-1800s, when the upper crust of society would attend Easter services at various Fifth Avenue churches then stroll outside afterward, showing off their new spring outfits and hats. Average citizens started showing up along Fifth Avenue to check out the action