statenisland

That's not pipe for installation, it looks like an old well they dug out.

Tribes and/or occasion weren't indicated?

This is the 1913 groundbreaking for the never-completed National American Indian Memorial: en.wikipedia.org/wiki/National_American_Indian_Memorial

Date is 22 February 1913 according to the Wikipedia article on the event. More on Rodman Wanamaker. The article on the memorial mentioned above mentions: Also in attendance were 32 or 33 American Indian chiefs, including Red Hawk and Two Moons. Red Hawk was a Sioux and Two Moons was a Cheyenne. It would probably be possible to identify some of the more prominent Native Americans in the photos. Red Hawk was very famous--a photo of him from 1907 is here, and a short Wikipedia article with photo of Two Moons. I have made some tentative identifications on the photo, but it is hard to say. There is a New York Times article from 23 February 1913 about this event. It is quite lengthy, with some biographical information on the participants, but there are no detailed captions for the photos.

rockcreek and cotinis: Thanks to both of you for the additional information about this photograph and the event it depicts. It is difficult to make definitive identifications of all the individuals shown, but we can at the least add more details about the ceremony to this record.

The tall native third from right is Jack Redcloud, son of the famous Lakota chief who was known as Redcloud and who won a war with the United States in 1866--Redcloud's War, of course. Redcloud, the father, was a great man, brave, wise, stubborn, and infamous in his youth for killing the tyrant Bull Bear.

These are incredibly ugly.