[3][better source needed] The department was established in 1903 with the enactment of California's first probation laws.

Captain Augustus C. Dodds was appointed as first chief probation officer of Los Angeles County.

known as Central Juvenile Hall, was established on Eastlake Avenue in the city of Los Angeles in 1912.

[4] By 1920, the department had 27 deputy probation officers, handling 1,893 juvenile court petitions and 690 adult cases each month.

[4] By 1940, the department has 108 staff members handling 4,063 juvenile and 5,299 adult probation cases.

[4] Five hundred field services deputy probation officers "investigated 25,000 adult and 16,500 juvenile cases each year and supervised 24,500 adult and 15,000 juvenile probationers from 11 area offices," and an additional hundred deputies "worked with almost 1,000 boys in 10 camps.

[4] In 1962, the department's headquarters moved to the new Los Angeles County Hall of Records at Civic Center, and Leland C. Carter was appointed chief probation officer.