The men were former members of the Mormon Battalion, and they were blazing trail for a company of Saints - many of whom were from the ship Brooklyn which had arrived in San Francisco with members of the Church on their way to the Salt Lake Valley just a few months before. The plaque to the right of the fountain notes it's creation (the plaque was placed by the Sons of the Utah Pioneers), and has the date 1967 on it, which sounds like about the time the fountain was built. I think my brothers Mike and Joe were involved with it, and they would know better.
Also among this company were other members of the Mormon Battalion who has been working for John Sutter at his mill in Coloma when gold was discovered. One of the massacred men (Ezra Allen) was carrying a pouch of gold that the Indians inadvertently left behind. The pouch was eventually taken to the dead man's widow in Salt Lake, and she had a wedding ring made with some of it, using the rest to help provide for herself and her children.
The first two photos were taken facing east, and the last one is facing north. You can't see it too well in this photo (unless you click on it to enlarge), but the source of the spring is covered by a little shed sitting right between the two large trees you can see. The spring now comes down to the right of this photo, and with such a wet year as we've had, is gushing quite well even this late in the season. Just above the shed is the actual trail cut by these pioneers, which is still easily traceable through the trees along the ridge. Fascinating history.