Congress has the power to establish universal federal rules of naturalization, to define how immigrants become citizens. Naturalization laws and immigration laws are two different animals. The former pertains to how we treat immigrants who are here, the latter to how we restrict and/or punish entry of foreigners, if at all. The first federal US law to restrict immigration was the Chinese Exclusion Act of 1882. Until then, we basically had an open borders policy with no civil or criminal penalties for people entering the US. In other words, there was no such thing as “illegal immigration”, just immigration. Today we would call these people “illegal immigrants”, those who violated a civil statute by illegal entry or by overstaying a visa and are subject to a possible deportation order. So…up until 1882, in the absence of any immigration laws, would-be “illegal” immigrants were welcome here by default as long as they otherwise obeyed the law. EDIT: They were also eligible for naturalization after a certain time regardless of how they arrived here, in stark contrast to today’s laws. Therefore, in response to your original comment, we were effectively a melting pot of what we would now call “illegals” for at least the first century of our existence and most of the second century for those who were white.