In a significant development for anyone who conducts historical research, the New York Times announced today that its online archive of news stories now includes all articles back to Sept. 18, 1851, the day the paper started publishing. Until now, the archives went back only to 1981. Searches for pre-1981 articles produce PDF files showing articles exactly as they appeared in the newspaper. You must be a TimesSelect subscriber to access the archives, which is free for print subscribers and $49.95 a year for others.