Elk Rock Island represents part of an ancient volcano that erupted about 40 million years ago. The large, jagged rocks (Waverly Heights basalt) found throughout the island were formed by lava flows, and may be the oldest exposed rock in the Portland area. The island contains seven distinct habitats, including wetlands, forests, and grasslands. Across the river, there are high cliffs which are Elk Rock proper.
A Native American legend holds that this was a good spot to stampede a herd of elk over the cliff, collected below by dugout canoes. The island gets its name from being near Elk Rock. Elk Rock Island was part of the original donation land claim of Milwaukie pioneer Lot Whitcomb and was known as Lot Whitcomb Island during the 1860s. It went through six owners before Scottish grain exporter and Portland businessman Peter Kerr (1862-1957) acquired the property in 1910 from the Rock Island Club, which operated a dance hall on the island. He gave the island to the City of Portland with the requirement that it be preserved in its natural state. As Kerr put it, "Preserve it as a pretty place for all to enjoy."
The island is accessible by a rustic trail that passes through the city of Milwaukie's Spring Park Natural Area. At the posted coordinates, a few feet away and below the river channel marker, you will find a plaque with the answers to fill in the following blanks. Terrain rating based on needing to navigate some large basalt rocks.
1. Let the year of the first date on the plaque equal a.aaa
2. Let the year of the second date equal b.bbb
Now some simple math. N45 24.218 + a.aaa W122 36.916 + b.bbb
These coordinates will take you to the cache. Please put it back so that it blends in well with its surroundings to keep this one safe from muggles. There is a benchmark loggable on geocaching.com located near the plaque at a slightly higher elevation (RD2614). Also be on the lookout for poison oak, as it is sometimes present on the island. Cache placed in 2003 by Hopalong & HobbleAlong Cachedy, adopted by Papa+2, and adopted by glorieme in March 2020.