The aims of the SPTL project include a demonstration that incorporation of dc superconducting transinission lines into the present US electrical utility power system is not only feasible but would lead to capital and operating economies compared with either conventional cable systems or superconducting ac lines, whenever large blocks of power are to be transmitted over long distances. The impact on the environment is minimal. The demonstration model is a line 1000 km long capable of carrying 5 GW of power, the type useful for carrying power from the Four Corners production complex to large urban areas in Phoenix, San Diego, or Los Angeles. The experiment includes data on superconducting samples, critical current measurements, test bed parameters, and power engineering studies. Experimental progress and planning are reported. (MCW)