Meningitis remains a significant cause of morbidity and mortality in the United States despite advances in vaccination, antimicrobial therapy, and critical care. However, long-term national mortality patterns across demographic and geographic subgroups remain incompletely characterized. This study evaluated temporal trends in meningitis-associated mortality among U.S. adults aged ≥25 years from 1999 to 2024 using the Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research (CDC WONDER) Multiple Cause of Death database. Death certificates listing meningitis as either the underlying cause or a contributing cause of death were identified using ICD-10 codes to capture meningitis-associated mortality. Age-adjusted mortality rates (AAMRs) per 100,000 population were calculated using the 2000 U.S. standard population. Temporal trends were assessed using Joinpoint regression to estimate annual percent change (APC) and average annual percent change (AAPC). Across the study period, meningitis-associated mortality demonstrated an early decline followed by stabilization and more recent increases in several subgroups. AAMRs decreased significantly from 1999 to 2001 (APC: −14.09%; p = 0.0029) and from 2001 to 2013 (APC: −4.74%; p < 0.000001), followed by a significant increase from 2013 to 2024 (APC: 1.78%; p = 0.0059). Despite these later increases, the overall AAPC across the full study period remained significantly negative (AAPC: −2.73%; p < 0.000001). Earlier analyses using shorter observation windows did not demonstrate a statistically significant overall trend; the significance observed in the present analysis reflects the inclusion of extended mortality data through 2024. Mortality rates were consistently higher among males and adults aged ≥65 years. Non-Hispanic Black individuals experienced increasing mortality after 2013, while Hispanic individuals demonstrated a sustained increase across the entire study period. Regional analyses showed recent increases in the Northeast, South, and West, while non-metropolitan areas did not experience statistically significant improvement through 2020. In summary, meningitis-associated mortality among U.S. adults declined significantly during the early study years but has shown stabilization and recent increases in several demographic and geographic subgroups since approximately 2013. Although overall mortality across the full study period remains lower than baseline levels, these emerging disparities highlight the importance of continued surveillance and targeted public health interventions.