This study quantifies differences in vegetation richness, composition, and structure between sites where fire has been excluded for 20 years and frequently burned sites in a Pinus palustris (Longleaf Pine) community within the Upland Island Wilderness in eastern Texas. Sixty plots were allocated equally between two sites: Upland Island, where fire had been excluded, and Boykin Spring, where fires were frequent. Plots were stratified within 3 relative topographic positions: lower slopes, upper slopes, and ridges. We collected data on vegetation within four strata (herbaceous, woody understory, mid-story, overstory) and on site parameters. Compared to the frequently burned site, the fire-excluded site had lower herbaceous species richness and cover, greater cover by shrubs and other pines in the understory and midstory, a denser midstory, and less Longleaf Pine regeneration. Overall, vegetation differences did not appear to be shaped by any underlying local edaphic and physiographic gradients. Our data demonstrated the effectiveness of a burning regime in maintaining and possibly recreating historic stand structure and diversity. It may be necessary to increase burning frequency to once every 2–3 years at Upland Island to reduce hardwood re-sprouts from emerging into the understory and midstory strata.