We also report here on the initial benchmarking of Parsley to show its improved accuracy relative to its predecessor for a wide variety of properties, especially energetics and geometries relative to gas phase quantum chemical calculations. The quantum chemical benchmarks, which cover more than 2,000 molecules and probe the quality of optimized geometries and relative conformer energies, show substantially better performance relative to SMIRNOFF99Frosst. For the condensed-phase properties, which span density, dielectric constant, heat of vaporization, excess molar volume, and enthalpy of mixing, no dramatic performance differences relative to SMIRNOFF99Frosst were noted in this release, and the overall accuracy is similar to that of GAFF; this was expected as nonbonded parameter optimization was not included as part of this work. In addition, as a reality check for the critical application area of computer-aided drug design, we report Parsley's favorable performance in benchmark protein-ligand binding free energy calculations covering 199 protein-ligand pairs, along with comparative results for other small molecule force fields. Importantly, the infrastructure described here establishes a foundation for going far beyond Parsley, through the ongoing creation of a series of continually improving, open, small molecule force fields. The process reported here in the OpenFF 1.0.0 release continues in subsequent releases (OpenFF 1.1, 1.2 and 1.3) which will be described in follow-up work.