Beginning in 1885, Keith taught mathematics at Mount Holyoke, and then became the school's first full-time teacher in the physics department there.

Holyoke in order to increase awareness among students of the growing field of physics.

[5] Keith investigated the physics of heat transmission in gases at low temperatures.

[1][5] Keith was a charter member of the American Physical Society, helping to establish the group in 1899.

[1] Keith and Isabelle Stone of Vasser were the only two women in attendance at the founding of the group.