The Canadian Galactic Plane Survey (CGPS) is a major initiative to improve our understanding of physical states and interactions in the Interstellar Medium (ISM) in our Galaxy. In 1995 we set out to create arcminute-resolution images of the major constituents of the ISM. We have (i) captured in action the flow of material and energy from the disk to the halo of the Galaxy, (ii) revealed detailed coupling of stellar winds to the ISM, (iii) laid the groundwork for statistical studies of the turbulent morphology of the ISM, (iv) shown that polarimetry provides a new window on the magneto-ionic medium in the Galaxy, and (v) discovered the first stages of star formation, where the Galactic spiral shock is driving formation of molecular gas from atomic clouds. Based on the results of the first five years, the CGPS Consortium proposes a Phase 2, designed to probe new questions. Over the period 2000 to 2005 the Consortium will tackle three major goals: (i) an extensive investigation of the disk-halo interaction, (ii) completion of the study of the Local spiral arm, where many astrophysical processes can be observed in great detail, and (iii) the first detailed mapping of atomic gas in a major star-forming region, the nearby Cepheus complex, which is forming stars over a wide range of masses.