The cold H I phase of the ISM often appears as H I self-absorption (HISA) against warmer H I emission. IGPS HISA features have been identified over most of the first and second quadrants with carefully-tested algorithms. The HISA feature population can now be studied systematically in terms of its observed properties. Weak absorption is found everywhere that HISA can occur and may arise from turbulence. Stronger HISA is concentrated into coherent structures, many of which appear to trace spiral density waves and perhaps evolving gas downstream of spiral shocks. The strong HISA implies cold gas temperatures that are difficult to maintain without molecular cooling. We are measuring the CO and dust content of the HISA clouds to investigate this problem.