The National Day of Mourning is an annual demonstration, held on the fourth Thursday in November, that aims to educate the public about Native Americans in the United States, notably the Wampanoag and other tribes of the Eastern United States; dispel myths surrounding the Thanksgiving story in the United States; and raise awareness toward historical and ongoing struggles facing Native American tribes. The first National Day of Mourning demonstration was held in 1970 after Frank "Wamsutta" James's speaking invitation was rescinded from a Massachusetts Thanksgiving Day celebration commemorating the 350th anniversary of the landing of the Mayflower. James instead delivered his speech on Cole's Hill in Plymouth, Massachusetts next to a statue of Ousamequin, where he described Native American perspectives on the Thanksgiving celebrations. The gathering became an annual event organized by the United American Indians of New England (UAINE) and coincides with both Thanksgiving Day in the United States and with Unthanksgiving Day, an annual ceremony held on Alcatraz Island in California.

Unthanksgiving Day, also known as The Indigenous Peoples Sunrise Ceremony, is an event held on Alcatraz Island in San Francisco Bay to honor the indigenous peoples of the Americas and promote their rights. It coincides with the National Day of Mourning held in Massachusetts. The Alcatraz ceremony has been held annually since 1975 to commemorate the protest event of 1969, where the Alcatraz-Red Power Movement (ARPM) occupied the island. It is organized by the International Indian Treaty Council and American Indian Contemporary Arts.