The figures are preliminary and don't include what Border Patrol agents call "got aways." Officials say it was the highest monthly total since at least 2006.
The head of the U.S. Border Patrol said her agents are spending more and more of their time dealing with families with children who need food and medical care.
Days before the midterm elections, President Trump threatened to close the Southwest border to asylum-seekers. Immigration experts say his remarks were filled with false and misleading statements.
A record number of migrant families arrived at the Southwest border over the last year, despite the Trump administration's effort to deter illegal immigration by separating families at the border.
According to U.S. Customs and Border Protection, the number of people arrested or "deemed inadmissible" along the Southwest border continued to drop in March, after showing sharp declines in February.
