The Columbia Bottomlands, a Southern floodplain forest formation on the upper Texas coast, historically covered over 283,000 ha but has since been reduced to 25% of its former extent. The importance of this regional ecosystem as critical stopover and staging habitat for Nearctic-Neotropical migratory landbirds gave rise to the Columbia Bottomlands Conservation Plan, an active land acquisition and conservation program administered by the U.S. Fish and Wildlife Service and its governmental and non-governmental partners. The Plan seeks to establish an integrated network of protected tracts as representative examples of the regional landscape, and thus conserve ecosystem integrity, function, heterogeneity, and biological diversity. We describe the Conservation Plan and its progress to date, and we summarize data on the plant composition of a typical preserved tract. Vegetation sampling at the Dance Bayou Unit, a mature forest remnant, revealed a mosaic of species composition across habitats varying in microtopography, soil type, and flooding pattern. The Dance Bayou study is a formative step in developing guidelines for future plant inventories, for site characterization in aid of land acquisition, and for restoration targets. As threats from urban development accelerate, intensified efforts may be needed to reach the Conservation Plan goal of protecting 10% of the original ecosystem extent.