Simulations predict that galaxy evolution is regulated by the accretion, expulsion, cooling, and heating of gas in the halos that surround galaxies out to hundreds of kiloparsecs. Distant quasars can be used to backlight and detect circumgalactic gas in absorption, and to date, tens of thousands of intervening absorbers have been detected in large spectroscopic quasar surveys. However, the observational challenges of connecting absorbing gas to their host galaxies has long limited the utility of even vast quasar absorption samples toward a better observational understanding of how the stellar populations and gaseous halos of galaxies co-evolve. I will present results from a Hubble Space Telescope program studying the circumgalactic medium of galaxies at redshift z~1.2. The slitless nature of the infrared grism observations enable efficient measurements of the group environments, inclinations, and star formation rates for a sizable sample of galaxies, facilitating correlations between these properties and circumgalactic absorption. The results provide compelling insights into the origins of cold, metal-enriched halo gas and the wind-driving potential of their host galaxies near the peak epoch of star formation.