Mud brick test walls were constructed at Fort Selden State Monument, New Mexico, USA in 1985 in order to monitor the erosional rates of various amendments to mud plaster, the capillary rise in selected wall bases, and the impact of precipitation on wall caps. These experiments will yield insights into the long term preservation requirements of historic and contemporary earthen architecture. This status report describes the effects of weathering on the experimental walls after twenty two months of exposure. The project will continue for a period of ten years.