History of Site

Geological History

The area around Rocky Butte was scoured by the cataclysmic Bretz floods from Glacial Lake Missoula around 13,000 to 15,000 years ago.  These catastrophic floods and the formation of Glacial Lake Missoula are referred to as the "Ice Age Floods."There are very thick layers of sand and gravel below the site, deposited by these Ice Age Floods when they ran into Rocky Butte.

Terrain

The terrain at the site varies considerably.  The large hill at the south end near the Gateway MAX station is composed mostly of construction debris deposited there when the interchange ramps were modified to accomodate the I-205 freeway.

Rocky Butte Jail

Prior to 1983, the Multnomah County jail was an antiquated, fortresslike ediface constructed of huge granite blocks from a quarry on the east side of Rocky Butte.