Background: Prospective randomized trials have demonstrated that neoadjuvant chemoradiation improves local control and results in a higher rate of sphincter-sparing surgery for patients with locally advanced rectal cancer. However, neoadjuvant therapy utilization and population-based outcomes are not well defined. Methods: Adults with stage II/III rectal adenocarcinoma within the National Cancer Data Base undergoing surgery between 2006-2012 were analyzed. Patients were grouped by type of neoadjuvant therapy received: no therapy, chemotherapy only, radiotherapy only, or concomitant chemoradiation. Multivariable modeling was used to compare perioperative outcomes and overall survival between groups. Results: Among 32,978 patients included, 9,714 (29.5%) received no neoadjuvant therapy, 890 (2.7%) chemotherapy only, 1,170 (3.5%) radiotherapy only, and 21,204 (64.3%) concomitant chemoradiation. 5-year overall survival among groups was 62%, 69%, 71%, and 74%, respectively. Compared to no therapy, chemotherapy or radiotherapy alone was not associated with any differences in perioperative or oncologic outcomes (all p > 0.05). With adjustment for patient and disease characteristics, neoadjuvant chemoradiation was associated with a lower likelihood of margin positivity (OR 0.74, p < 0.001), need for permanent colostomy (OR 0.77, 95% CI 0.70-0.85, p < 0.001), 30-day mortality (OR 0.67, p = 0.003), and overall survival (HR 0.69, p < 0.001). When compared to chemotherapy or radiotherapy alone, neoadjuvant chemoradiation was still associated with improved overall survival (vs. chemotherapy: HR 0.83, p = 0.04; vs. radiotherapy: HR 0.75, p < 0.001). Conclusions: Neoadjuvant chemoradiation, not chemotherapy or radiotherapy alone, is important for sphincter-preservation and survival for patients with locally advanced rectal cancer. Despite this finding, one third of patients with locally advanced rectal cancer are failing to receive this therapy in the United States.