The origin of the highest energy particles ever observed, ultrahigh energy cosmic rays (UHECRs), has been a longstanding open question in astroparticle physics. Despite significant observational challenges, the Pierre Auger Observatory has provided unprecedented, precision measurements of the spectrum of UHECRs and composition-related observables. These measurements, combined with multimessenger data from IceCube and Fermi-LAT, have the potential to shed light on the nature of UHECR sources. In this talk, I will discuss studies which leverage a realistic, phenomenological model of UHECR sources and multimessenger data, and what they tell us about the environments host to UHECR accelerators and the connection between UHECRs and the TeV-PeV astrophysical neutrino flux.