Read this secondary source that describes the black codes.
When were black codes enacted?

Before the war ended

Right after the Civil War

A year after the war ended
No sooner had the Civil War ended than most Southern states adopted what came to be known as Black Codes or Black Laws. These codes were aimed at limiting the economic and physical freedom of former slaves.

Jim Crow in America
The Library of Congress

Black codes were enacted right after the Civil War.

Explanation:

Black Codes were laws created by former Confederate states after the Civil War to weaken the status of blacks in those states. Laws began to be created in 1865 with the passage of the 13th Amendment to the Constitution in the United States, which officially liberated all black slaves.

Black Codes had time to be created for more than a year before Congress, with a Republican party opposed to slavery in the majority, passed the Civil Rights Act and the 14th and 15th Amendments to the Constitution. In the late 1870s, however, the position of blacks weakened again as racist extremism, led by the Ku Klux Klan, intensified.

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