Overview of U.S. Immigration Laws Regulating the Admission and Exclusion of Aliens at the Border [Updated June 10, 2019] [open pdf - 697KB]
From the Document: "Reports of a 'migrant caravan' traveling from Central America to the United States have sparked considerable attention on the treatment of non-U.S. nationals (aliens) without legal immigration status who are arrested at or near the U.S.-Mexico border. The 'caravan' comprises aliens primarily from Honduras, many of whom purportedly came to the United States to escape crime and political instability in their native countries. In recent months, there has been a marked increase in the number of apprehensions of aliens at the border seeking to unlawfully enter the country, with roughly three times as many border apprehensions in May 2018 compared to the same time last year."
CRS Legal Sidebar, LSB10150
Congressional Research Service: https://crsreports.congress.gov/