While the Lambda-CDM cosmological model is remarkably effective at describing the Universe as a whole, foundational questions remain.  Where did the primordial fluctuations come from and why are they so uniform?  What is causing the present-day accelerated expansion?  Maps of large-scale structure at different epochs can address these questions.  I will present results from the BICEP/Keck cosmic microwave background experiment, which leads the search for B-mode polarization from an inflationary expansion at the earliest moments of time.  I will then discuss a promising new cosmological probe -- millimeter-wave line intensity mapping -- which will measure large-scale structure well into the first billion years of the Universe and constrain the nature of dark energy.  These observables have benefited from recent advances in millimeter-wave technology, and I will describe how next-generation instrumentation will improve our understanding of the early Universe over the next ten years.