Background: NCCN guidelines recommend concurrent chemoradiation (cCRT) as initial treatment for unresectable, stage III non-small cell lung cancer (NSCLC). The objective of this study is to evaluate cCRT rates over time and geographic region, and to identify patient and facility characteristics associated with receipt of cCRT. Methods: Electronic medical record data from the Veterans Affairs (VA) Corporate Data Warehouse and data from the VA Central Cancer Registry were used to identify veterans who were diagnosed with stage III NSCLC from 2013 to 2017. Patients survived at least 45 days post-diagnosis, did not have lung resection within 180 days, had at least two visits of VA cancer care, received chemotherapy (CT) and/or radiotherapy (RT) within 120 days of diagnosis, and had their records reviewed by a cancer registrar. cCRT was defined as initiation of CT and RT within 14 days of each other; while sequential chemoradiation (sCRT) was initiation more than 14 days apart. Generalized mixed models accounting for clustering by VA facility were used to determine factors associated with cCRT receipt compared to other treatment (sCRT, CT only, or RT only). Results: From 2013 to 2017, 3,414 veterans with stage III NSCLC met inclusion criteria. Fifty-five percent of these veterans received cCRT, 15% received sCRT, 14% received RT only, and 16% received CT only. The percentage of veterans receiving cCRT increased from 51% in 2013 to 62% in 2017. cCRT rates were highest in the Midwest (60%) and lowest in the West (51%). Fifty-six percent of whites received cCRT vs 53% of non-whites. Factors associated with increased odds of receipt of cCRT compared to any other treatment include white race (adjusted OR [aOR]=1.24; 95% CI: 1.01-1.53), later diagnosis year (2017 vs 2013: aOR=1.67; 95% CI: 1.28-2.17; 2016 vs 2013: aOR=1.36; 95% CI: 1.06-1.75), and facility with on-site radiation oncology services (aOR=1.43; 95% CI:1.02-1.99). Factors associated with decreased odds of cCRT receipt compared to any other treatment included increasing age (aOR per 10 years=0.66; 95% CI: 0.59-0.74) and Charlson-Deyo comorbidity score (aOR=0.94; 95% CI: 0.91-0.97). Conclusions: Receipt of cCRT in veterans with unresectable, stage III NSCLC slightly increased from 2013 to 2017, and varied across Census region and facility. Veterans who were older, non-white, had more comorbidities, or were seen at a facility without on-site radiation oncology services were less likely to receive cCRT.