TEVISTON, Calif. — Bertha Mae Beavers remembers hearing stories as a child about the promises of California, a place so rich with jobs and opportunity that money, she was told, “grew on trees.” So in the summer of 1946 she said goodbye to her family of sharecroppers in Oklahoma and set out for a piece of it.

For decades she labored in the Central Valley’s vast cotton and grape fields, where eventually her children joined her. Looking back, Ms. Beavers, who turned 90 this year, has sometimes wondered why she left home at all. It was all the same trouble, she said.

Amid a vast migration during the early 20th century, tens of thousands of black people like Ms. Beavers came to California’s farm country from far-off states in the Cotton Belt and the Dust Bowl.

And as in other parts of the United States, black migrants were met with Jim Crow-style racism: “Whites Only” signs, curfews and discriminatory practices by banks. Often, the only places black families could settle were on arid acres on the outskirts of cultivated farmland — places like Teviston, the all-black colony where Ms. Beavers raised 12 children in “a two-bedroom shack” with no bathrooms or running water.