Royal catchfly (Silene regia, Caryophyllaceae) is a rare, tap-rooted, perennial forb known to occupy Midwestern prairies, glades, and savannas, which are increasingly fragmented. Though not federally listed, it is recognized as rare, threatened, or endangered in six states. We resurveyed 15 populations identified in 1980s–1990s monitoring at Wilson's Creek National Battlefield, Republic, MO. Abundance at each site was collected in 6 y (1988–1989, 1998–2000, 2019); measures of plant height and stems browsed were collected in 4 y (1998–2000, 2019). Fire history and precipitation were also explored. Mean royal catchfly abundance per population declined significantly over the study period, and only five of 15 populations supported extant populations in 2019. Year, site location, and the interaction between the two were highly significant factors in explaining variation of height measures and proportion of stems browsed. Plant height was significantly higher in 2019 than any other year, corresponding with overgrowth of competing vegetation and a wet spring. Prescribed fires became less frequent over the study period, and the mean fire return interval was higher than the historical regime of the region (9.7 y vs. 4–8 y). The decline of royal catchfly at Wilson's Creek National Battlefield and similar sites points to the need for fire management and restoration of prairie and savanna ecosystems for the persistence of this rare species.