Why was inter-racial marriage illegal is some parts of the USA for a long time?

As a patriotic American it truly disgusts me that such a law was ever passed. It is almost as disgusting as slavery and the genocide of American Indians. One of the authors of the Constitution named Thomas Jefferson even loved a beautiful Black woman. America is a great and free country. Why did our ancestors do so many shameful things ?Why was inter-racial marriage illegal is some parts of the USA for a long time?as a Patriotic American i also find this is disgusting and never should have happened but it did. Dr. King was a great man for struggling for integration

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