The civil rights act of 1866 was significant because it

The Civil Right Act of 1866 has a great significance in the history. It is due to the fact that it was the first law being passed by the Federal to protect the Rights of all Civilians living in America.  

Actually after the American civil war, many people from Africa were brought in the state, and Government wanted to give them equal rights. So this legislation was passed by Congress in 1865 and was vetoed by the President Andrew Johnson.