Florissant National Monument is known for it's fossils from the Eocene epoch. The Eocene was the time between about 34 and 56 million years ago. Because of the environment and the organisms that existed at the time, Florissant is particularly well-known for its plant and insect fossils. Especially prominent in the monument are petrified redwood stumps. Even though there have been misguided attempts at removing the stumps in the past, some successful, some not, there are a handful of these large fossils that still remain for you to experience.
Because most of the organisms were fossilized in the fine ash from a nearby volcanic eruption, there are some fossils in Florissant that are almost never found. Mosses are one of these rare finds. Mosses do not have the hard parts that are usually fossilized, like bones and shells and woody tissue, so they are about as rare as finding a fossilized jellyfish.
To get to the point where things could be so well-preserved, a few things had to happen. First, a lake had to be formed. This happened at the Florissant site because a volcano caused mud flows that came down and dammed-up a stream, creating a natural reservoir. Next, plants had to grow around the lake. This happened because this is what usually happens around areas with water. When the plant community became lush, this attracted many insects and other animals. Fish, of course, would occupy the lake itself. Then, the ash comes into play. At this point, a different type of volcanic eruption had to occur. This time, instead of causing a mud flow, a volcano further away spewed large amounts of fine ash into the air, which settled on the area around the lake and in the lake itself. After a series of eruptions in a short period of time, there was enough ash to completely fill the lake. Plants parts and insects ended up in the lake and got covered by the ash, and fish were already in the lake. The ash compacted into rock before the organisms could decompose and that is why there are so many fossils found in the area.
In addition to being a world-renowned fossil site, Florissant is also in a beautiful location within the shadow of Pikes Peak. Pikes Peak is one of the big three mountains on Colorado's front range. The summit of Pikes Peak is actually the lowest in elevation between itself (14,115'), Mt. Evans (14,271') and Long's Peak (14,259'), but it seems to be higher because it is closer to the relative flatness of the high plains to the east. There's a reason it was the location where the song "America The Beautiful" was penned by Kathy Bates. Pikes Peak is the "purple mountain majesties above the fruited plain."