To characterize the geographic distribution of United States (US) headache subspecialists in 2021 compared to 2012 and analyze trends in distribution of and growth by geography. Headache disorders are the second-highest cause of disease burden worldwide. Historically, headache disorders have been treated by primary care and emergency physicians, often suboptimally. Our 2012 study identified further disparities in geographic distribution of United Council for Neurologic Subspecialties (UCNS)-certified headache subspecialists. This correlational population study explores the current geographic distribution of and changes in subspecialists by aggregating data from the UCNS, National Health Interview Survey, US Census, Bureau of Economic Analysis, and American Community Survey. In 2021, there were 692 UCNS-certified headache subspecialists. There continued to be higher subspecialist density in the Northeast (1:34,678) and Midwest (1:55,005), with the highest density in Vermont (1:12,510) and Connecticut (1:20,419). The highest absolute subspecialist increases were in the South (99), California (35), and Texas (25). The highest relative subspecialist increases were in the West (105%), Vermont (500%), and Mississippi (500%). The univariable regressions showed significant associations between number of subspecialists and adult headache population (R2 =0.797, p < 0.001), between subspecialist density and personal income (R2 =0.935, p=0.033), and between growth in subspecialists and poverty rate (R2 =0.553, p=0.022). However, the multivariable regressions showed that only the adult population was significantly associated with number of subspecialists (adjusted R2 =0.806, p < 0.001). Overall, there has been substantial growth in the number of UCNS-certified headache subspecialists in the US, especially relative to growth in adult headache population. Subspecialist density continues to be highest in the Northeast and is associated with higher per capita personal income. However, there has been encouraging growth in geographies that previously had little to no access. These findings represent positive progress, but there is more to be done to both increase access to optimal headache care by subspecialists nationally and decrease geographic disparities in access to care.