The mountain is composed of mesozoic ultramafic rock, predominantly serpentinized peridotite.

[5] The summit rises to an elevation of 9,037 feet (2,754 m), and is the highest point in Trinity County, the ninth most prominent peak in California, and the highest summit west of Interstate 5 in the United States.

The mountain receives heavy snowfall during the winter due to its altitude.

[6] The mountain is named in honor of Olive Paddock Eddy, who is mistakenly held to be the first woman to climb Mount Shasta.

Nelson Harvey Eddy arrived in the area from New York State in 1856.