... become known as the Utah War. (From Saints: Volume 2, chapter 17, emphasis added)

On July 24, 1857, the tenth anniversary of the Saints’ arrival in the valley, the Smoot family joined Brigham Young and two thousand other Saints for a picnic at a mountain lake east of Salt Lake City. Brass bands from various settlements played as the Saints spent the morning fishing, dancing, and visiting with each other. American flags flew from the tops of two tall trees. Throughout the morning, Saints fired cannons, watched the territorial militia drill, and heard speeches.

Around noon, however, Abraham Smoot and Porter Rockwell rode into camp, interrupting the festivities. Abraham had just returned from a Church business trip to the eastern United States. On the way, he had seen freight wagons traveling west to supply an army of fifteen hundred troops the president was now officially sending to Utah with a new governor. The government had also stopped mail service to Utah Territory, effectively cutting off communication between the Saints and the East.

I think it's fascinating that they were celebrating with patriotic symbols when they learned of a federal army marching on them due to their supposed rebellion. Also interesting that patriotism has been part of the celebrations since the beginning.