Montgomery's "Mad Men" modern buildings - are they worth protecting? But to Clare Lise Kelly, a historic-preservation planner for Montgomery County, and to other architectural experts, the office building at Georgia Avenue and Cameron Street is a shining example of International style. It's time, they say, for it and other "mid-century modern" buildings and homes - those with sleek, boxy designs from the 1950s and 1960s - to be considered for historic preservation. "The challenge is always preserving the recent past," Kelly said. It's easy to look at things from 100 years ago and see them as historic. . . . If we don't act now to assess resources from this time period, they'll be gone, and then it's too late to say, "That apartment complex was really special." " Popular interest in mid-century architecture and interior design has surged in the past few years with the success of the "Mad Men" TV series. But architectural preservationists began paying closer attention over the past decade as more modernist buildings passed the 50-year mark, traditionally the minimum age for consideration as historic. Preserving some of that past, experts say, is especially important now, as areas such as White Flint in Montgomery and Tysons Corner in Fairfax County continue to transform from sprawling suburbs into more urban nodes of high-rise buildings clustered around transit stations. Many of the newer developments, they say, feature more traditional architecture because they are designed to re-create the feel of the more walkable, old-fashioned Main Street. Kelly said she realizes that some people consider modernist buildings too young - and, in some cases, too plain or ugly - to warrant protection. It's not about age or looks, she said. It's about preserving critical pieces of architectural history from the post-World War II population and building boom that transformed suburbs such as Montgomery from rural bedroom communities into dense subdivisions and commercial districts. County planners have begun building their first database of mid-century modern buildings and subdivisions. The "Montgomery Modern" architectural survey, Kelly said, will ensure that the most significant structures survive. Montgomery is especially fertile ground for mid-century modern architecture. In the county, as many new homes and buildings took root during the first decade after World War II as had been built in its entire prewar history, Kelly said. The buildings generally lack classical details such as columns and ornamentation, and often have construction materials - concrete, glass panels, steel frames - embedded in the design. Mid-century modern houses typically have open spaces, a casual feel and extra-large windows to mesh living spaces with nature.