With its grandiose and imposing features, the Second Empire architectural style became popular as a symbol of strength and permanence among both public buildings and private homes.

The style originated in France, with the name referring to Napoleon III. Ruling the country as an emperor between 1852 and 1870, Napoleon III put particular focus on rebuilding Paris into a city of striking buildings and spacious avenues. The structures' styles migrated elsewhere in Europe and to the United States after a popular exhibition in Paris in 1855.

Some of the most recognizable features of the Second Empire style are derived from earlier styles. The Pennsylvania Historical and Museum Commission says the distinctive mansard roof on these structures is named for the architect Francois Mansart, whose designs appeared in the 17th century.

Wentworth Inc., an architectural design firm in Chevy Chase, Maryland, says the Second Empire style shares some similarities with Italianate buildings. Some building owners achieved a Second Empire appearance in established Queen Anne buildings by renovating them to include additional floors and a mansard roof.

The style was generally used for larger structures, making it a good fit for both private and public buildings in the prosperous years after the Civil War. Frederick Koeper and Marcus Whiffen, in their 1981 textbook "American Architecture Volume 2: 1860-1976," say Second Empire was often used in hotels, train stations, and government buildings. The style was sometimes known as the General Grant style, since many of the public buildings built during Ulysses S. Grant's presidency were in the Second Empire style.

One of the most well-known examples of the style is Philadelphia City Hall, a towering municipal building which was built between 1871 and 1881. The Eisenhower Executive Office Building, which includes offices for White House staff in Washington, D.C., is another impressive Second Empire structure.

Not all Second Empire buildings are gigantic or ostentatious. Wentworth Inc. says the style is well-suited for townhouses, since the mansard roof allows the buildings to look taller. Home improvement professional Bob Vila says the Second Empire style was especially popular in cities, since it allowed an efficient use of living space on constricted lots.

As the most recognizable feature of a Second Empire structure, the mansard roof is also highly functional. George Hopkins, in his 2009 book "Creating Your Architectural Style," says the roof has a steep pitch and flat top. Wentworth Inc. says the roof shapes have varied over the years, including concave and convex designs. The roof is typically covered with slate, and the upper cornice is sometimes surrounded by an ornamental iron crest. Occasionally, a tower is also present in the front central area of the roof.

The steep pitch and flat roof create plenty of space on the upper floor, meaning the area under the mansard roof can easily be used as extra living space rather than simply an attic. Dormer windows are often incorporated into the slope of the roof, although they do not project far from the surface.

Like an Italianate building, a Second Empire structure includes brackets under the eaves. The Washington State Department of Archaeology and Historic Preservation says other similarities with this style include bay windows and ornate embellishments to the tops of windows and doors.

Custom molding on the building's exterior are often heightened by the eye-catching qualities of a Second Empire structure's exterior. The interior of the house may feature such ornamental designs as pillars, curving staircases, and decorative designs on the walls.

The entrance to the home is easily recognizable, typically featuring a wide single door or a set of double doors. This entrance is usually sheltered under a porch and reached by crossing a pavilion and ascending a set of stairs.

Windows are tall and elongated. Their typical arrangement of panes is two-over-two or one-over-one.

Despite the impressive façade, Second Empire buildings generally had a simple footprint. The Washington State Department of Archaeology and Historic Preservation says these structures were usually symmetrical with a square, rectangular, or box form; occasionally they were L-shaped.

Though it was well-received during affluent times, Second Empire homes were much harder to build during downturns in the economy. Hopkins says the style fell out of favor after the Panic of 1873, a depression which lasted about four years.