The last known address can not be released from the veteran's record.
You can contact the American Legion, VFW, or other veteran's orgnizations. They may have sources for locating veterans (for example through reunions).
The National Archives does not have the present addresses of former service personnel or their survivors on file. The Federal agency most likely to have such addresses is the Department of Veterans Affairs (VA). The VA can forward a message from you to the veteran, providing the veteran has filed a claim with VA, and they have an address on record. To forward a message, please write your message and place it in an unsealed, stamped envelope. Also include a note to the VA explaining who it is you are trying to reach and add as much identifying information as you have. Place all of this in another envelope addressed to the nearest Veterans Affairs Regional Office (you can find the address at
If the veteran is in their records, your message to the veteran will be sealed and the envelope addressed to the address they have on file for the veteran. Please note that the veteran may not have informed the VA of a change of address, so they cannot guarantee receipt of your message. If the veteran receives your note, it is then up to the veteran to contact you.
Another thing - you could search Facebook for the veteran or the actual unit they were assigned to.
Also, the unit may have a website (search Google).