The Claytonville (“Canyon lime”) field, located in Fisher County, Texas, is a large Pennsylvanian carbonate buildup along the western margin of the Eastern shelf (Midland Basin). Since its discovery in 1952, the field has produced more than 66 million bbl of oil and 86.7 billion cubic feet of gas. Originally characterized as one large carbonate reef, later unpublished core descriptions encompass a wide variety of carbonate facies, including a lack of boundstone fabrics that is typical of many modern and ancient reefs. Although much previous research has been conducted on larger nearby reefs (Horseshoe atoll), very little has been published on the characteristics of smaller, time-equivalent buildups (Claytonville). Here, we present wire-line log, whole-core, and three-dimensional (3-D) seismic data to characterize and interpret the facies and overall morphology of the Claytonville buildup. Geologic and 3-D seismic mapping show that the buildup consists of an elongated, northeast-oriented ridge-like structure approximately 5 mi long and 1–3 mi across, consisting of three separate pinnacle-like buildups, the product of several large-scale growth cycles. Core analysis shows that internally the buildup consists of a series of small-scale, upward-shoaling units. Individual units include lower-energy crinoidal-rich lime wackestones and packstones grading upward into higher-energy skeletal and oolitic lime grainstones. A better understanding of these smaller Pennsylvanian carbonate buildups is important not only from a standpoint of future production potential but also as an analogue for similar buildups in the region and time-equivalent carbonate buildups elsewhere in the world.