Dataset for journal article, Improved Simulation of Particle Number Concentrations Over the US: Integrating a Size-Resolved Advanced Particle Microphysics Model Into CMAQ. Observed aerosol number concentrations, particle size distributions, and CCN are available via F. Yu, Luo, et al. (2020), Marinescu et al. (2019), and Perkins et al. (2022). Part of data of particle size distributions and number concentrations were accessed at https://ebas-data.nilu.no/Default.aspx and https://csl.noaa.gov/groups/csl7/measurements/2013senex/. Figures were plotted using MATLAB R2023b and NCAR Command Language (NCL) version 6.3.0. MATLAB is available under its license at https://www.mathworks.com/products/matlab.html and NCL can be accessed under its license at https://www.ncl.ucar.edu/. This dataset is not publicly accessible because: Lead is outside of EPA and only EPA author is no longer with the Agency. It can be accessed through the following means: Contact the corresponding author of the journal article, Dr. Fangqun Yu, fyu@albany.edu. Format: Dataset details not available. This dataset is associated with the following publication: Mao, J., F. Yu, B. Murphy, J. An, Y. Zhang, G. Luo, S. Lin, and A.G. Hallar. Improved Simulation of Particle Number Concentrations Over the US: Integrating a Size-Resolved Advanced Particle Microphysics Model Into CMAQ. JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES. American Geophysical Union, Washington, DC, USA, 130(16): e2025JD044021, (2025).