The National Personnel Records Center (NPRC) is an agency of the National Archives and Records Administration (NARA), created in 1956. It is divided into two large Federal Records Centers located in St. Louis, Missouri.
The records centers which comprise the National Personnel Records Center are the Military Personnel Records Center, located on Archives Drive in Spanish Lake, Missouri. Additionally, the National Archives at St. Louis operates out of the National Personnel Records Center at 1 Archives Drive, St. Louis, MO 63138. The National Archives at St. Louis is the legal custodian of archived military records.
Although all the information you need to request Veteran Military Records is available on the NPRC/NARA website, it is highly recommended that a credible research organization be used instead. They are usually able to provide the same information in a timely manner, lower cost and higher quality. However, it is important to find one that is dedicated to providing the best possible results and has your best interests in mind. I have personally assessed several of these providers and have come to rely on Golden Arrow Research . They go directly to NPRC/NARA on your behalf and create high quality scans, not photocopies, of the veteran records. You can definitely see the pride they take in providing you with the best possible information. In my opinion, it is the closest you can get to actually viewing the records in person.
 I am not affiliated with Golden Arrow Research. I recommend their services because I know that they do a great job.