Via The Washington Post:

U.S. authorities detained more than 1.7 million migrants along the Mexico border during the 2021 fiscal year that ended in September, and arrests by the Border Patrol soared to the highest levels ever recorded, according to unpublished U.S. Customs and Border Protection data obtained by The Washington Post.

Illegal crossings began rising last year but skyrocketed in the months after President Biden took office. As CBP arrests increased this past spring, Biden described the rise as consistent with historical seasonal norms. But the busiest months came during the sweltering heat of July and August, when more than 200,000 migrants were taken into custody.