Federal - Ubiquitous up and down the East Coast, Federal style architecture dates from the late 1700s and coincided with a reawakening of interest in classical Greek and Roman culture. There's an appealing plainness and symmetry about many Federal houses. Red brick is the most common building material. Doors often have sidelights and fanlights and whatever is going on the right side of the façade is echoed on the left. Double-hung windows with shutters are common, as is a certain amount of restrained classical ornamentation around cornices, doors, and windows.
Greek Revival - This style is predominantly found in the Midwest, South, New England, and Mid-Atlantic regions, though you may spot subtypes in parts of California. Its popularity in the 1800s stemmed from archeological findings of the time, indicating that the Grecians had spawned Roman culture. American architects also favored the style for political reasons: the War of 1812 cast England in an unfavorable light; and public sentiment favored the Greeks in their war for independence in the 1820s.
Identify the style by its entry, full-height, or full-building width porches, entryway columns sized in scale to the porch type, and a front door surrounded by narrow rectangular windows. Roofs are generally gabled or hipped. Roof cornices sport a wide trim. The front-gable found in one subtype became a common feature in Midwestern and Northeastern residential architecture well into the 20th century. The townhouse variation is made up of narrow, urban homes that don't always feature porches. Look for townhouses in Boston, Galveston, Texas, Mobile, Ala., New York, Philadelphia, Richmond, Va., and Savannah, Ga.
Queen Anne - A sub-style of the late Victorian era, Queen Anne is a collection of coquettish detailing and eclectic materials. Steep cross-gabled roofs, towers, and vertical windows are all typical of a Queen Anne home. Inventive, multistory floor plans often include projecting wings, several porches and balconies, and multiple chimneys with decorative chimney pots.
Wooden "gingerbread" trim in scrolled and rounded "fish scale" patterns frequently graces gables and porches. Massive cut stone foundations are typical of period houses. Created by English architect Richard Norman Shaw, the style was popularized after the Civil War by architect Henry Hobson Richardson and spread rapidly, especially in the South and West.
Contemporary - You know them by their odd-sized and often tall windows, their lack of ornamentation, and their unusual mixtures of wall materials--stone, brick, and wood, for instance. Architects designed Contemporary-style homes (in the Modern family) between 1950 and 1970, and created two versions: the flat-roof and gabled types. The latter is often characterized by exposed beams.