The origin of the slope-oriented linear patterns of ridges and pools in many northern fens is currently not well understood. Most studies of this phenomenon have been confined to one site and have tried to identify a single biological or physical process responsible for pattern formation. The topographic setting, size, slope, peat depth, age, vegetation, and ridge/pool morphology of two patterned peatlands in the Upper Peninsula of Michigan are described. The two sites experience the same climate and both are situated in glacial meltwater channels. Shingleton Fen is smaller, younger, and less steeply sloped, with shallower peat, smaller and more sharply delimited strings and flarks, lower pH, and more distinctly differentiated string and flark plant communities than Creighton Marsh. Analysis of these differences in light of some of the current hypotheses of pattern formation indicates that these single-process models are inadequate. A biogeomorphological approach, integrating both physical and biological processes, is required to explain the initiation and development of these features.