How many illegal aliens came to USA during trump's first time as president?
Executive summary
There is no single, authoritative count in the public record that answers “how many illegal aliens came to the U.S. during Trump’s first presidency (2017–2021),” because the government does not publish a net inflow figure for people who enter unlawfully and remain — only encounter, apprehension and removal statistics that measure different things [1]. Available reporting instead offers multiple partial metrics and conflicting signals: some show sharp drops in border encounters at the outset of his term, others show high detention and arrest activity in later years, and academic analysts emphasize that enforcement and policy changes — as well as the pandemic — altered both flows and measurement [2] [3] [4].
1. Why the question can’t be answered with a single number
The U.S. government does not compile or publish a net “illegal arrivals who stayed” statistic, so researchers and reporters substitute proxies such as Customs and Border Protection encounter counts, Border Patrol apprehensions, ICE interior arrests and formal removals — each of which captures different slices of migration and enforcement and therefore cannot be summed to produce a reliable net inflow number [1]. PBS and other fact‑checkers have cautioned that comparing raw daily encounter averages between different administrations can be misleading because weather, policy shifts and other factors change both crossings and the ability to detect them [2].
2. What the partial metrics show for 2017–2020
Early in Trump’s first term, border encounters reported by officials fell sharply after he entered office — a decline that multiple outlets documented and that the administration highlighted — but analysts warn such short‑term drops can reflect seasonal or administrative factors rather than durable reductions in underlying migration [2]. At the same time, interior immigration enforcement (ICE administrative arrests) increased in fiscal 2017 and 2018 after executive orders expanded priorities, with ICE arrests rising roughly 30% in fiscal 2017 before easing again in later years [5]. Detention activity and many enforcement metrics peaked mid‑term: for example, people detained by ICE reached a high point in 2019 (about 510,860 detainee instances reported in journalistic summaries) even as removals and interior enforcement fluctuated [3].
3. Policy and pandemic effects that complicate counting
The Trump administration significantly curtailed lawful immigration pathways (reductions in green cards and non‑immigrant visas) and imposed restrictions in 2020 tied to COVID‑19 that dramatically altered flows and the issuance of immigration documents, which in turn affected the unauthorized population and official statistics [4]. Cato and other analysts stress that these policy changes — along with a “virtual halt” in some admissions during the pandemic — make year‑to‑year comparisons fraught and obscure net inflows versus temporary crossings or returns [4].
4. What scholars and reporters say about the undocumented population trend
Academic and journalistic efforts have focused on shifts in apprehensions, removals and enforcement rather than producing a single cumulative “arrivals” tally; Pew, Cato and major outlets have therefore described trends — initial border declines, heightened interior arrests in certain years, a detention peak in 2019 and later declines or stabilization — rather than a precise count of people who entered illegally and remained [5] [3] [4]. Where estimates exist, they rely on modeling and proxy measures that produce ranges and contested results rather than a definitive total [1].
5. Bottom line and limits of available evidence
The sources reviewed do not provide a definitive number of “illegal aliens who came to the U.S.” during Trump’s first term; instead they document partial indicators (encounters, ICE arrests, detentions and policy impacts) that point to changing flows and enforcement intensity but cannot be converted reliably into a single net inflow figure [1] [5] [2]. Any precise claim about the total number of people who entered unlawfully and remained during 2017–2021 goes beyond the reporting provided here; to produce such a number would require demographic modeling and datasets not included in the cited sources.