South Dakota Gov. Kristi Noem’s ascension to Homeland Security secretary-in-waiting came as a surprise in some quarters. After all, the former member of Congress hasn’t worked in the department and doesn’t have a law enforcement background.

President-elect Donald Trump has selected South Dakota Gov. Kristi Noem as his next secretary of the Department of Homeland Security, according to two people familiar with the selection.

Ms. Noem, the governor of South Dakota, would play a major role in carrying out the president-elect’s promises to crack down on the border and deport millions of people.