Did your ancestors immigrate to the United States between 1846 and 1851? Do you have Japanese ancestry? Was anyone in your family held as a prisoner of war during World War II or the Korean War? Did your relatives help build the Panama Canal? These questions may sound unrelated, but if you can answer yes to any one of them, you might find valuable family history clues in the National Archives and Records Administration's (NARA) <www.archives.gov> latest online offering: the Access to Archival Databases (AAD) system. Through 350 databases, AAD provides access to nearly 50 million records created by more than 20 federal agencies.

Among AAD's 350 databases are several data files of special interest to genealogists. Go to the AAD Web site <www.archives.gov/aad>, click the Search button, and then click on People to access resources dealing with immigrants, Japanese-American internees, prisoners of war, wartime casualties and Panama Canal Zone deaths. Here's a look at 10 of those files and the clues they hold:

• Combat Area Casualties Database names 58,965 US military officers and soldiers who died or who were missing in action or prisoners of war in Southeast Asia from 1956 to 1998.