ALMO — As towers of granite greeted emigrants taking the California Trail through Idaho in the mid-1800s, hundreds of pioneers felt compelled to leave their mark in the valley’s silent City of Rocks.

Many of the signatures remain, finger-painted in axle grease mostly on the south wall of Camp Rock, one of the first outcroppings of granite that emigrants encountered along the trail. The signatures are dated from 1843 to 1882.

A decades-old photograph of the rock wall displayed at the site shows hundreds of signatures of pioneers, many of which have faded or eroded away.

It’s part of the natural process, said City of Rocks National Reserve Superintendent Wallace Keck.

Standing inside an open cave at the base of Camp Rock, Keck explained how emigrants used the cave as shelter. Some stood in their wagons to reach high on the wall of the cave to sign in for prosperity.

Some of the signatures have weathered nearly two centuries of storms. Others have seemingly evaporated over time, the effect of rain, wind, freezing and thawing, and ultraviolet light.

“We do not try to protect the signatures from these natural effects,” Keck said. “But we have them well-documented in pictures and information.

“The signatures will continue to fade over time until they disappear altogether perhaps, a hundred years from now.”