SOMETIMES A SINGLE step speaks powerfully and succinctly of a legacy, a history and a future.

On Tuesday morning, W. Richard West Jr., will take a momentous first step. West, of the Southern Cheyenne tribe from Oklahoma, will lead an expected 20,000 people from native communities throughout the Western Hemisphere on a long-awaited walk across the Mall. As founding director of the National Museum of the American Indian, West knows the importance of symbolism and ceremony. It has taken more than two decades of negotiations, fundraising, lobbying and planning to reach the long-awaited museum opening on the Mall, which takes place on Tuesday.

"This is not just a gathering and coming together," West said. "There is something about procession that is very important. In much of native life and native culture, procession attaches to ceremony. For example, when we begin a powwow, a large intertribal dance gathering, it always begins with a grand entry. It is a ceremonial point of beginning. It is a way of commemorating cultural memory and remembrance. For me, this [procession] has all the markers of that . . . inaugurating this remarkable institution in Washington, D.C."

When the museum opens on Tuesday, the grand Native Nations Procession will gather Native Americans in a mile-long pageant. Then a six-day First Americans Festival on the Mall continues with performances on six stages, featuring 300 dancers, singers, storytellers, instrument- and regalia-makers, even a comedian.

Although the procession may not appear to be a choreographed dance, the prospect of bringing together so many representatives from differing native cultures takes the logistical know-how and insight of a dancemaker. With more than 15,000 participants signed up at press time and registration ongoing, the procession, which begins at 9:30 a.m. and concludes across the Mall at noon where the opening ceremony takes place, is likely the largest gathering of Native Americans from multiple tribes in recorded history.

That the procession travels from west to east, from the Smithsonian Castle to the foot of the U.S. Capitol (the museum is at Fourth Street and Independence Avenue SW, near the Capitol), is no accident. "Its direction is not lightly chosen," West noted. "Fortunately the Mall sits on an east-west axis. But for many people in the native communities, including Cheyenne and the native people who live in this area, our lodges open to the east. The east is at the very point of beginning."

Jim Pepper Henry, assistant director of community services for the museum, is charged with fine-tuning the logistics of the event. Henry, a member of the Kaw Nation of north central Oklahoma, explained that the walk "is a symbolic movement of people from west to east, which is significant because a great many Native Americans were pushed back to the west. This is an important metaphor for us: walking back to the east." Henry pondered this symbolic homecoming. "Even though many Native Americans have been removed from their ancestral homelands . . . this [procession] is the one key event that's inclusive of everyone. It's a reaffirmation that native peoples are here, we exist and we've come together to celebrate this historic occasion."

Immediately after the ceremony, the real dancing begins. The National Congress of American Indians will sponsor a Native American social dance on the Mall, where the gathered tribes can share and exchange their cultural traditions. Unlike specific tribal ceremonial dances, which are usually closed to outsiders, social dances are meant for all and reflect the variety and diversity of Native American cultures. There are men's dances, women's dances, group circle dances and couple dances. Without the competitive spirit of the powwow, the social dance celebrates special occasions, such as the museum opening.

David R. Boxley will arrive in Washington this weekend with 12 members of the Git-Hoan Dancers from Kingston, Wash., who have been talking about the museum and procession for months. Representing the Tsimshian, Haida and Tlingit nations from southeast Alaska, the Git-Hoan Dancers perform an exciting style of dance drama that features storytelling and masks. "These dances," Boxley explained, "mark important events, like becoming a chief, marriage, adoption, a new home, a girl's first menses. They are the cornerstone of our society, and they help tell the stories of our people."

Museum director West has his own story about learning traditional Cheyenne dances as a 6-year-old from his father. "I'll never forget what my father told me: 'You will always know who you are as long as you keep dancing.' "

NATIVE NATIONS PROCESSION -- Tuesday, rain or shine. Staging begins at 8 a.m. on the Mall (14th Street, between Madison and Jefferson drives). Walk is from 9:30 to noon. Traditional dress is encouraged. You need not be a member of a Native American tribe to participate. Nations assemble in alphabetical order with independent and supporting individuals and organizations lining up last. Register online through Monday at www.americanindian.si.edu or on-site Tuesday at 7.

SOCIAL DANCE -- Tuesday at 1 on the Mall, sponsored by the National Congress of American Indians. For a detailed schedule of dance events, visit the Web site or call 202-633-1000.

The Navajo Dine Tah Dancers will perform at the Dance Circle during the First Americans Festival on the Mall.