Keith began working in the theater at a young age and in 1893 was put in charge of bookings for Keith's Theatre, which opened the following year.

When he turned 30, his father gifted him the Bijou Theatre in Philadelphia.

[6] In 1908, Keith served as acting general manager of the United Booking Office while E. F. Albee recovered from injuries suffered in an automobile accident.

[10] In 1915, Keith was elected president of the Boston Athletic Association.

($80,920,000 in 2024 dollars),[12][13] A lifelong bachelor, his business holdings were inherited by Albee and other business partners, while his personal assets were given to Cardinal William Henry O'Connell and Harvard College.