Despite its low elevation relative to peaks higher in the Cascades, it is a famous and dramatic landmark due to its topographic prominence.

The first recorded ascent of Mount Index (the main peak) was on October 29, 1911, by H. B. Hinman, Ernest Martin, Lee Pickett, George E. Wright.

[4] Mount Index is located in the marine west coast climate zone of western North America.

As a result, the west side of the North Cascades experiences high precipitation, especially during the winter months in the form of snowfall.

[5] Due to its temperate climate and proximity to the Pacific Ocean, areas west of the Cascade Crest very rarely experience temperatures below 0 °F (−18 °C) or above 80 °F (27 °C).