Who are immigrants to the US, where do they come from and where do they live?

Immigrants to the U.S. increasingly arrive like these people, seeking asylum at a formal border crossing, rather than trying to sneak across the border. Carlos Moreno/NurPhoto via Getty Images

Undocumented immigration is a key issue in American politics, but it can be hard to nail down the basic facts about who these immigrants are, where they live and how their numbers have changed in the past few decades.

I study the demographics of the U.S. immigrant population and have seen how the data has changed over time. Here are some basics to set the stage as President Donald Trump begins his second term in office vowing to crack down hard on immigrants, including by conducting mass deportations.