Headline: What's behind the historic, 'serious challenge' at the southern borderLink: https://abcnews.go.com/Politics/happening-border-congress-grapples-immigration-d…Publication Date: Thursday, December 21, 2023Primary Source: ABC NewsOther Sources: MSNNon-Cato Author: Quinn OwenType: articleFormat: Newspaper (Print)Nature of Mention: citedScholar: CatoResearch Area: Immigration and Labor MarketsSubjects: illegal immigration at the southern border