More than 100,000 people are expected to turn out for this Sunday’s 108th Dorchester Day Parade, which starts at 1 p.m. from the corner of Richmond Street and Dorchester Avenue in Lower Mills. The parade— packed with marching bands, floats and politicians— will follow a three-mile route up Dot Ave. to Columbia Road.

The parade, organized by a volunteer committee that works throughout the year to prepare for the event, will include appearances by the two top contenders for the US Senate: Both Senator Scott Brown and his main Democratic challenger plan to march.

Dorchester Day originated in 1904 as a commemoration of the original settlement of the town by English colonists in 1630— one month before Boston was incorporated. In more recent times, Dorchester Day has become a celebration of the multi-cultural mix that is modern-day Dorchester— with an emphasis on bands, dancers and colorful floats that highlight the neighborhood’s robust civic and cultural life.

Among the dignitaries who will be part of the parade’s first division will be Chief Marshal Ralph Browne, a veteran of the Korean War; the honorary Mayor of Dorchester Katie Hurley, who raised thousands of dollars to help cover the costs of the event; and the Young Miss and Little Miss Dorchester contest winners, MyChalia Sanfilippo, 12, and Delia O’Toole, 7, respectively