Background/Objectives: To examine if head injury (HI) is associated with age at ALS diagnosis in the United States. Methods: In this cross-sectional populationf-based analysis, we identified patients with ALS who were registered from 2015 to 2023 who completed the Registry’s head trauma survey module. The association between HI and age at ALS diagnosis was assessed using multivariate analysis. Results: Of the 3424 respondents, 56.6% had experienced a HI. The adjusted odds ratio (aOR) for an ALS diagnosis before age 60 years for patients with a HI was 1.24 (95% CI, 1.07–1.45). One or two HIs had an aOR of 1.15 (95% CI, 0.97–1.36), and five or more HIs had an aOR of 1.58 (95% CI, 1.19–2.09). HI before age 18 years yielded an aOR of 2.03 (95% CI, 1.53–2.70) as well as HI between the ages of 18 and 30 years (aOR = 1.48, 95% CI: 1.06–2.06)). When narrowing the analysis to patients with HI before age 18 compared with patients with no HI, we found an association with HI that led to an emergency department or hospital visit (aOR = 1.50 (95% CI: 1.21–1.86)). Conclusions: In this cross-sectional analysis of ALS patients, HIs occurring in childhood and early adulthood and the number of HIs increased the odds of being diagnosed before age 60 years. These results suggest that HI continues to be a risk factor for ALS and could be associated with a younger age of diagnosis.