The claim has two core elements: (1) that the Williamsport facility near Hagerstown was 'the first' Trump prison camp (in the warehouse-conversion class) planned to open; and (2) that it was stopped by a lawsuit brought by the state of Maryland. Element (2) is fully and multiply confirmed at Tier 1–4. Maryland Attorney General Anthony Brown filed suit on February 23, 2026; a TRO halted construction in March 2026; and a full preliminary injunction was granted on April 15, 2026, twelve days before the air date, directly blocking DHS/ICE from converting the Williamsport warehouse into a detention facility while the lawsuit continues. The Center for Biological Diversity independently confirmed that construction would already have begun absent Maryland's legal action, establishing the causal nexus. Element (1) — the 'first' characterization — is where a modest imprecision resides. Reporting confirms that the Maryland warehouse was among the very earliest ICE warehouse purchases (January 2026), and Maryland's was described as the first state-level lawsuit over the warehouse conversion program. However, multiple warehouse sites across Maryland, Pennsylvania, and Arizona were purchased essentially simultaneously in January 2026, and earlier detention facilities of a different model (tent camps, notably Camp East Montana at Fort Bliss) predate the warehouse conversion initiative entirely. Maddow's framing of 'prison camps' contextually refers to the new class of warehouse-conversion detention facilities, and within that category the Williamsport facility was indeed the first to be litigated and halted — but 'first planned to open' is not definitively established by the evidence over competing warehouse sites. This is an identifiable but minor imprecision that does not reverse the directional meaning of the claim (per MOSTLY_TRUE boundary test: if corrected to 'one of the first,' a reasonable viewer would still agree with the overall point). The core assertion — Williamsport warehouse, halted by Maryland's lawsuit — is well-supported and accurate. MOSTLY_TRUE is the appropriate nomination.