This dissertation consists of several projects designed to further our understanding of galaxies and galactic structures associated with intervening quasar absorption lines -- i.e., those selected via gas cross section.Surveys for MgII absorption were conducted utilizing QSO spectra from the Sloan Digital Sky Survey and data collected at the 6.5m Multiple Mirror Telescope Observatory on Mount Hopkins, AZ. The first survey expands the number of studied MgII systems by an order of magnitude, while the second extends the statistics to weaker systems and lower redshifts. The results provide high-precision measurements of the statistics and evolution of MgII absorbers. It is shown that the distribution of rest equivalent width steepens with decreasing redshift, especially at redshifts z<1, such that the total absorption co-moving cross section decreases at a rate proportional torest equivalent width. This is interpreted as an evolution in the kinematic properties of the absorbing galaxy population. Evidence for multiple physical populations comprising MgII absorbers is presented and discussed.Early survey results were used to investigate the cosmic neutral-gas-phase metallicity and dust content. QSO spectra selected due to the presence of strong intervening MgII absorption were stacked in the absorption rest frame to create high signal-to-noise ratio composites with which to measure Zn and Cr abundances. It was found that metallicity of high-N(HI) gas is highly correlated with the kinematic properties of galaxies and both metallicity and dust content for these systems increase with decreasing redshift.Two projects were completed that involved the imaging of six low-redshift damped Lyman-alpha galaxies. Detailed properties of the identified absorber galaxies are described. They are shown to be drawn from a variety of morphological types with a range of luminosities, environments, and impact parameters
