At the Indigenous People’s Sunrise Gathering on Alcatraz.
The tradition was born out of the occupation in the 1960s (abridged here via Wikipedia) and particularly fascinating given the current Occupy Movement:
According to the IAT, the Treaty of Fort Laramie (1868) between the U.S. and the Sioux returned all retired, abandoned or out-of-use federal land to the Native people from whom it was acquired. Since Alcatraz penitentiary had been closed on March 21, 1963, and the island had been declared surplus federal property in 1964, a number of Red Power activists felt the island qualified for a reclamation.
On March 8, 1964, a small group of Sioux demonstrated by occupying the island for four hours… this demonstration was an extension of already prevalent Bay Area street theater used to raise awareness. The protesters were publicly offering the federal government the same amount for the land that the government had initially offered them; at 47 cents per acre, this amounted to $9.40 for the entire rocky island, or $6.54 for the twelve usable acres.