Migration flows to the U.S. from Mexico are surging for the third time in seven years under Republican and Democratic presidents — and for similar reasons. Numbers grew steadily over President Donald Trump's final months in office but demographics shifted more recently. Families and children traveling alone, who enjoy more legal protections and require greater care than adults, have accounted for 29% of all Border Patrol encounters in February, up from 13% two months earlier. The Biden administration is rapidly opening new holding centers to speed children's release in the United States.