Members of the Cowboy and Indian Alliance rode their horses through the streets of Washington, D.C. dressed in full costume. Then they gathered at the National Mall at their encampment.
The demonstration was part of a week-long series of events by farmers, ranchers and tribes called "Reject and Protect."
Opponents of the pipeline believe the environmental risks from the pipeline are too high. Supporters, on the other hand, argue there's only minimal risk to the environment and that the energy and economic benefits are more important.