What percentage of the southern border remains unfenced or without a physical barrier as of 2025?
Executive summary
Using U.S. Customs and Border Protection’s public “Smart Wall” summary of barrier mileage along the 1,954‑mile U.S.–Mexico border, roughly 777 miles of physical barrier existed prior to January 20, 2025, implying about 1,177 miles — roughly 60 percent — remained without a constructed barrier as of early 2025 [1]. That headline percentage depends heavily on definitions (primary vs. secondary barriers, vehicle barriers, legacy fencing) and on whether “covered by detection technology” counts as effectively fenced; the underlying sources make these distinctions but do not offer a single authoritative percentage label [1] [2] [3].
1. The arithmetic behind the figure: CBP’s mileage totals and the 1,954‑mile baseline
CBP’s Smart Wall materials state the U.S.–Mexico border is about 1,954 miles long and list “Existing Barrier (prior to 1/20/2025)” of approximately 702 miles of primary wall plus about 75 miles of secondary wall — roughly 777 miles of constructed barrier — which leaves 1,177 miles unfilled by those barrier tallies [1]. Dividing that unfenced mileage (1,177 miles) by the 1,954‑mile border yields an unfenced share of roughly 60 percent; this is a direct calculation from CBP’s own pre‑1/20/2025 numbers rather than an independent federal pronouncement of a percent unfenced [1].
2. Why “unfenced” is not a single, uncontested category
Multiple actors use different yardsticks: advocacy organizations and researchers distinguish primary pedestrian fencing from vehicle barriers and ad‑hoc or legacy fencing, and note that many stretches are “vehicle barriers” or low, climbable panels that critics say “hardly qualify” as a fence (FAIR) — meaning a mileage count can overstate effective denial if every physical impediment is treated equally [2]. CBP itself supplements gaps with detection technology — stating approximately 536 miles “without barrier will be covered by detection technology” — a programmatic choice that treats some unfenced segments as mitigated by sensors and surveillance rather than physical walls [1].
3. Reporting and oversight nuance: what federal reviews add
Government Accountability Office work has emphasized the complexity of counting and evaluating fencing — GAO has analyzed geospatial data adjustments, sector variation (for example, that a few sectors contain most primary pedestrian fencing) and the need for consistent assessment methods rather than headline mileage totals alone [4]. GAO and DHS reports also document that appropriations and obligations for barrier construction are uneven and paused at times, which affects how quickly miles change and why a single static percentage can be misleading without a date and definition [5].
4. Political programs, state efforts, and evolving construction through 2025
Federal and state programs were active in 2024–2025: CBP’s Smart Wall plan and related funding (including large appropriations in mid‑2025 for Smart Wall construction) indicated a renewed push to build in some segments, and states like Texas reported dozens of miles completed under state programs in early‑to‑mid 2025 — but those additions were incremental relative to the nearly 2,000‑mile border and do not eliminate the majority of unfenced mileage as reported by CBP prior to 1/20/2025 [3] [6] [1]. Legislative efforts such as the Build the Wall Act of 2025 reflect political momentum to convert more miles to barriers, underscoring that the unfenced percentage is a policy as well as a mapping fact [7].
5. Bottom line and caveats for readers
As of the CBP summary of barrier mileage that covers “Existing Barrier (prior to 1/20/2025),” about 60 percent of the southern border — roughly 1,177 of 1,954 miles — lacked the listed primary/secondary physical barriers; however, this numeric answer must be read with the caveat that agencies and analysts disagree on what constitutes an effective fence (primary vs. secondary vs. vehicle barrier vs. coverage by sensors), and the sources do not provide a single standardized “percent unfenced” label — the 60 percent figure is a straightforward calculation from CBP’s published mileages [1] [2] [4]. If a different operational definition (for example: counting vehicle barriers or sensor‑covered stretches as “fenced”) is used, the percentage will shift; the public sources supplied here do not converge on one definitive percentage under all reasonable definitions [1] [3].