When tracing ancestors across the centuries, kin are often clustered together in a similar locations, an economic situation, or an ethnic identity. A gateway ancestor is anyone with known or traceable ancestry from one specific group who marries into another group. Each immigrant from one country to another is a potential gateway, if his/her descendants can then trace his/her ancestry to the original country. Gateways can also occur when someone moves from one distinct social group into another or across distinct religious, economic, or racial barriers.
In the United States, however, the term “gateway ancestor” most commonly is used to refer to colonial immigrants whose ancestry can be traced in the Old World—specifically to gentry, nobility, or royalty.