Cast-iron architecture is a purely American invention, and the largest concentration of cast-iron buildings is in SOHO.

Practical, easy to maintain, durable, and inexpensive cast-iron buildings started appearing in the 1840s but gained popularity by the 1860s. Cast-iron storefronts were made from pre-fabricated molds and, therefore, were cheaper and faster to produce than the ones from stone. The cast-iron front could be easily divorced from the construction behind it, making it easy to apply to a building. One could pick a storefront of a building from a catalog, choosing the style of columns, dimensions, and decorative details. Cast iron allowed for making enlarged windows allowing a lot of light, which was advantageous for shops and storefronts. Cast-iron front could support a building’s structural weight without relying on bulky interior columns. Cast-iron buildings were virtually weatherproof; broken pieces could easily be recast and replaced.

Visually, cast-iron buildings were completely traditional and appealed to the aesthetic tastes of the times. They often appeared in the form of Renaissance Palazzi, with a series of arches and rows of columns.

The cast-iron front, painted to look stone-made, can be hard to tell from a stone facade. To determine if the building is cast-iron, one could use a magnet or look closely at the decoration detail: metal allowed for more delicate detailing than stone carvings. Also, if a cast-iron piece was missing, there was no sign of breakage since each piece is secured by screws.

It’s all summed up in the preface to 1865 Daniel Badger’s Illustrations of Iron Architecture,

“It must be evident that whatever architectural forms can be carved or wrought in wood or stone or other materials can also be faithfully reproduced in iron. Besides, iron is capable of finer sharpness of outline, and more elaborate ornamentation and finish; and it may be added that it is not so liable to disintegration, by exposure to the elements, as other substances …. The cost of highly-wrought forms in stone or marble, executed with the chisel, is often fatal to their use; but they may be executed in iron at a comparatively small outlay, and thus placed within the reach of those who desire to gratify their own love of art, or cultivate the public taste”.

The cast-iron construction fad was short-lived and ended in the 1880s; however, some consider cast-iron buildings a precursor to modern skyscrapers. Despite the excitement about the technology and its many practical advantages, the cast-iron structures had limitations. It turned out that they were vulnerable to fire. Also, their construction was rigid; the parts were held together by bolts set up by hand. Cast-iron buildings were soon replaced by steel-skeleton skyscrapers.

There are over 200 cast-iron facade buildings in SOHO.