from trails.com:
Echo Rock is a craggy old dacite plug located low on Ptarmigan Ridge just east of Observation Rock. It is one of the most visible of Mount Rainier's satellite peaks, especially when viewed from Seattle. For this reason, it used to be known as €œSeattle Rock.€ There's a reason it is called Echo Rock, which you will no doubt discover if you have chatty people in your group.
This plug is commonly climbed with it's neighbor, Observation Rock.
from Summitpost:
Close up views of some of the most impressive aspects of Mt. Rainier such as Curtis Ridge, Liberty Ridge, Ptarmigan Ridge, and Sunset Ridge, Carbon Glacier, Russell Glacier, North Mowich Glacier, Edmunds Glacier, and Liberty Cap Glacier, Willis Wall, Liberty Wall, and the Mowich Face.