You might want to check the slave laws. These same laws ruled free slaves.
Va wrote the first laws ruling the first 20 slaves that came to the Americas. All slave laws are based on these. Each new state took these same laws to another level.

1662 Va passed an act whereby a child born of a slave mother was also held to be a slave, regardless of its father.

This is proablly the main reason for intermarriage of free slaves.

These same slave laws ruled the free slave as well as slaves. Depending on the state and the year most had to have a sponser and register in order to stay in the area they lived. These are found in court records.

Quan