The District library's Washingtoniana division is a treasure trove of D.C. history How do you do it? How do you know so much about so many things? I give a knowing wink and walk away. Why should Answer Man give up his secrets for free? But for you, dear (paying) reader, I'm willing to share my technique. The truth is, I find someone who knows more than I do and ask him or her. Quite often, that person is a librarian. Amazingly, the same things librarians do for Answer Man - help ferret out information about our area - they'll do for you, too. And so today I'm launching a series of occasional columns exploring local history resources. Let's start with one of the biggest, shall we? That's the Washingtoniana division of the D.C. Public Library, ensconced on the third floor of the Martin Luther King Jr. Memorial Library downtown. It is usually Answer Man's first stop, whether to research a historic church or a historic dairy. On a recent visit, I found Joseph Duff near the microfilm readers. He was seated at a table covered with piles of reference books: "Freedom and Slavery Documents in the District of Columbia," "District of Columbia Free Negro Register: 1821-1861," probate records from 1801 to 1855, marriage records from 1870 to 1877. . . . Joseph is doing his family's genealogy. On this visit to Washingtoniana, he was tracking down information on Caleb Overton, a free black man from Charles County variously identified as Caleb Ovington and Caleb Othrington. "He's my fifth great-grandfather," said Joseph, 67, a retired civil rights lawyer who lives in Silver Spring. Black history is one of Washingtoniana's strengths. The division was founded in 1905 , when then-library director George F. Bowerman started collecting books related to the city's history. Since then, the holdings have grown to include some 60,000 books, 8,000 maps, 2,000 postcards, 5,000 linear feet of archival material and 1.3 million images. Among the pictures catalogued at Washingtoniana is the photo archive of the Washington Evening Star. The Star is on microfilm at Washingtoniana, too, along with The Post and such defunct papers as the Washington Herald and the Washington Times (the original Washington Times). African American papers are there, too. You can scan city directories, which once were like super-detailed phone books, complete with the occupation of each resident. Some of the material is digitized and searchable on your computer from home. That includes the Evening Star from 1852 to 1952, once searchable only via a handmade index. All you need is a D.C. library card, which you can get even if you don't live in the District. "People are loving having the Washington Star," said Kim Zablud, special collections manager and boss of the 12-person department. For decades, the Star was the city's leading newspaper, often besting the rag you're reading. The D.C. Commissioners" reports - some 61,000 pages of delightful detail on everything from the city's road repairs to its dogcatchers - will soon be going online. Answer Man often dips into Washingtoniana's invaluable vertical files, which are a bunch of newspaper clippings and other paper ephemera organized by subject matter. All sorts of people besides newspaper columnists and amateur genealogists use Washingtoniana. New homeowners curious about their abodes search building permits or consult colorful plat maps. An inordinate number, Kim said, are curious about whether crimes were ever committed in their houses. Students work on school projects. Academics hunker down with archival material, such as the papers of political gadfly and D.C. home rule activist Julius W. Hobson. Washingtoniana continues to collect and digitize, Kim said. The division is making a commitment to gathering oral histories, including of the March on Washington and U Street's days as a cultural crossroads. It's also hoping to carve out a niche in go-go music and the D.C. punk scenes. Washingtoniana is in the MLK Library at 901 G St. NW, across from the Gallery Place Metro. It's open 11 a.m. to 8 p.m. Monday through Thursday, 9:30 a.m. to 5:30 p.m. Fridays and Saturdays. Admission is free, though there's a charge for using the photocopiers. You'll probably get more out of your visit if you do a little research first. Go to the Web site dclibrary.org/research/ collections. Call or send an e-mail (202-727-1213; wash.dcpl@dc.gov) to give the librarians time to think about where to point you. And if you should see Answer Man sitting there, his head in a book or his eyes watery from staring at microfilm, please say hello. No such thing as dumb questions Don't worry. Answer Man is not abrogating his responsibility. He's happy to tackle your questions about the Washington area. Send them to answerman@washpost.com.