Sunday marks the last time the Rolling Thunder motorcycles will participate in the Memorial Day observance on the National Mall.

For many people, the group’s decades-long presence with the loud hum of their motorcycle engines has become synonymous with Memorial Day activities in Washington.

Rolling Thunder’s Ride for Freedom was designed to raise awareness of service people who have given their lives or are missing in action during U.S. military combat.

Rolling Thunder Executive Director Artie Miller says he has grown frustrated with dealing with the Pentagon in coordinating the annual Ride for Freedom on Memorial Day.

He says sponsors, participants and vendors were not allowed access to parking lots last year, even though Rolling Thunder said it had paid “exorbitant permit fees.”

In 2020, the nonprofit Rolling Thunder is asking its 90 local chapters to hold their own individual Memorial Day demonstrations with the intent of spreading the event and expanding participation. That’s why Miller doesn’t view this as the end of the event, but rather as a transformation of it.

U.S. Defense Department figures show that 83,000 American military personnel remain unaccounted for, and a large majority — about 73,000 — are from World War II. Upward of 7,700 are from the Korean War, and 1,600-plus are from the Vietnam War.