Thousands of people lined the streets as iconic balloons floated and marchers danced in celebration of the 91st Macy's Thanksgiving Day Parade. The American event made its way through 2.5 miles of Manhattan on a cold morning, with new faces and old favorites among its signature giant balloons. The parade is the largest one in the world and has been held since 1924. New York Police Department officers with assault weapons and portable radiation detectors were circulating among the crowds.