What caused the enactment of the fugitive slave act?

The Fugitive Slave Act of 1850 was enacted as part of the Compromise of 1850 to appease the South and preserve the Union. It required that escaped slaves be returned to their owners, even if they were found in free states. The act was a major source of tension between North and South and fueled anti-slavery sentiments in the years leading up to the Civil War.