If there's one notable architectural feature all Montrealers know and love (or hate, depending on the season), it's the city's many outdoor staircases. Eye-catching during the warmer months and altogether deadly in the winter, the sometimes-spiral-y staircases that stretch from apartments right onto the street are a Montreal icon.\nLargely unseen in any other North American city, outdoor staircases are entirely unique to Montreal. But as aesthetically pleasing as the iron staircases are, you've no doubt noted their impractical nature, especially in a city when the stairs are covered by a thick layer of ice for half of the year.\nAnd that's where the mystery of Montreal's outdoor staircases begins, a conundrum we're going to try and solve, even though it's something of a fruitless effort. Because no matter what, we can't go into the brains of builders in the early 1900s who built a majority of the exterior staircases found in Montreal, but we can speculate.\nBut before we delve into the myriad of possible reasons why Montreal has outdoor staircases, it's important to note and discuss another architectural feature of the city they are intrinsically linked to, namely plexes.\nA "plex," for those who aren't familiar with residential building terminology, is basically just a building with two or more stacked living units. Duplexes refer to a building with two apartments, triplexes for three, quadruplex for four, and so on. Actually, the "plex" term tends to stop at the four mark, but you get it.\nAnyone familiar with residential living options in Montreal knows how the plex-format is pretty much the standard; plexes are the most popular form of housing in Montreal.\nAnd anytime you see a plex, there is an outdoor staircase seen stretching from second-floor apartments and onto the street in such buildings. Outdoor staircases and plexes are a packaged deal, a fact that helps to explain most of the theories found below.\nA Mixing Of Cultures\nThe plex-format of buildings is something of a cultural fusion, noted David Hanna, a professor of geography at UQAM. Back in the 19th century, Scottish immigrants came into the city and brought with them the practice of piling residences atop each other. At the same time French-Canadians settlers came from the countryside into the city and utilized exterior stairways to link floors of their rural homes. Eventually the cultural architectural practices would fuse, resulting in the practice of individual outdoor staircases attached to each apartment in a plex.\nBuilding Space Setbacks\nWhen new housing units began popping up in the early 20th century, the City of Montreal enforced some regulations that limited the amount of distance between the foundation of a building and the sidewalk. This was done to ensure streets weren't crowded, but it also limited the amount of space available to an apartment unit. So, in order to free up some room, builders did away with indoor staircases and instead put them on the outside, thus providing more room without breaking any building regulations.\nTo Keep Montreal Clean\nA catalyst for the aforementioned building regulation forcing buildings to be a certain distance away from the street could have been sanitation concerns. Montreal's sanitation-situation was so bad in the early 1900s that the city was deemed a "hygienic disgrace to civilization." Dinu Bumbaru, a director at Heritage Montreal, has linked this sanitation concern to the by-law forcing buildings to be further away from the street, which then led to the practice of installing exterior stairways in order to free up space inside of each apartment.\nThe Frugal Landlord\nOne very real reason for Montreal's many staircases may be attributed to the very human desire of saving money. Landlords, you see, are responsible for heating all "common areas" of a building, and that extends to staircases. So, in order to save some cash, some theorize that landlords (or the original builders) built external staircases to circumvent that cost.\nAn Influx Of Rural Immigrants\nMontreal experienced a serious population boom during the late 19th and early 20th century, exactly around the time when outdoor staircases started popping up. Many of the newcomers to the city, as already mentioned, were from rural areas, and wanted to retain the same "feel" of their country homes in their new urban setting. In order to do so, they built homes that had their own entranceway, despite the fact that it was above or below another dwelling, using an exterior stairway to reinforce that aesthetic.\nBecause The Church\nThrowing away all of the economic and cultural factors that may have led to Montreal's abundance of exterior stairways, there is the very real possibility that religion was the driving factor behind the building practice. You see, a private, enclosed staircase would have been regarded as a space where any number of sins could go down, like a torrid love affair between a mail man and a married woman. So, in order to suppress potential sinful acts, outdoor staircases that everyone could see (and judge you upon) were encouraged by the Catholic church.