Final answer:
Yvonne Brathwaite Burke's first achievement was being elected as the first African American woman to represent California in the U.S. Congress.
Step-by-step explanation:
Yvonne Brathwaite Burke's first notable achievement was being elected as the first African American woman to represent California in the U.S. Congress. She was elected to the U.S. House of Representatives in 1972 and served until 1978. This was a significant milestone in American history and broke barriers for women of color in politics.