The Native American Sunrise Ceremony is held every Thanksgiving on Alcatraz Island.
It is an opportunity to commenorate and give thanks to the native people of this country.
The original Thanksgiving of 1621 was meant to give thanks for the harvest.
This harvest was possible because of the help that the native people of America gave to the Pilgrims.
The year before many Pilgrims had died due to starvation.
The native peoples taught the Pilgrims agricultural techniques that were successful.
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from http://sfpsociety.org/alcatraz.html