The United States' Endangered Species Act (ESA) is the world's foremost law for protecting species at risk of extinction; however, species must first be listed as threatened or endangered before receiving protection under the Act. We used an information theoretic approach to assess whether listing budget, policy phase (which was correlated with presidential administration), or both factors were associated with the number of species listed annually between 1983 and 2014. Annual listing rates were positively affected by larger listing budgets; policy phase also had a significant impact on annual listing rates after accounting for the effects of budget. However, the listing process for any one species spans multiple years, thus we also evaluated how taxonomic affiliation, the initiating organization, and lawsuits affected the amount of time 1338 listed species spent in review between 1973 and 2014. Species waited a median of 12.1 years to receive protection, with plants and invertebrates experiencing longer wait times than vertebrates. These process times exceed ESA deadlines, which are two years when initiated from a third party; this may perpetuate population declines and hinder recovery efforts. We observed that at the time of a lawsuit filling for either a proposed or final rule, species had waited, respectively, 4.19 and 0.70 years longer than species for which no lawsuits were filed, indicating lawsuits targeted species that experienced longer delays. We discuss how changes in ESA implementation over time interacted to produce high variability and often long wait times in the listing process. Our results indicated a positive role for both citizen petitions and budget increases to advance the listing process, thus hastening biodiversity protection.