Final answer:
The seizure of Alcatraz Island in 1969 was carried out by Native American activists who wanted to build an American Indian cultural center and raise awareness about their concerns.
Step-by-step explanation:
The seizure of Alcatraz Island in San Francisco Bay in 1969 was carried out by a group of Native American activists from various tribes. They landed on the island with the intention of building an American Indian cultural center. The occupation of the island lasted for more than a year and a half and aimed to bring attention to the concerns and grievances of Native American activists.