The Montclair Art Museum (MAM) is bringing back one of its most popular programs, Free Family Day: Powwow, to be held on Saturday, Sept. 25, from 1 to 5 p.m. A powwow is a Native American celebration that has evolved from a sacred ritual called a Grass Dance, part of a complex ceremony performed by warrior societies among various tribes of the Plains. Today, it is an event where all people can meet to honor American Indian culture and discover its rich legacies.