Medellín was established on the riverside as a mining and coffee town. The mining and coffee production led to the city’s industrialization, yet the city remained extremely isolated from the rest of the country. The only connection the city had was the Magdalena River (from which the Medellín River is an affluent). In the 1920s, the city witnessed the construction of a railroad (paralleling the river), and later on, the canalization of the Medellín River. Taking advantage of this new infrastructure, an industrial section grew next to the city center. A middle class began to emerge, and the “Escuela de Minas”, a large engineering school was founded. This School was essential in the city’s future development.
Around the later 1940s and early 1950s, the political violence reigned in Colombia’s countryside incited a large rural-urban migration ,and the Northeast sector of the valley was urbanized. Most of the urbanization consisted of poor farmers, which would quickly “invade” of land. These “invasions” (illegal occupation of the land), or informal settlements as they are preferably called, began to reflect the same configurations of the small towns from which the migrants came (Classical Spanish town planning, having a central plaza, church and everything developing orthogonally around). As such, even in the early stages of the settlement, the blocks are approximately 80mx80m with houses back to back; clear paths left open for circulation (Apparently, this type of settlement is very different from the one seen in Brazil for example, where the only open space that is respected is the soccer field- this makes the settlement much more difficult to upgrade without dislocating families).
An interesting fact is that people begin by establishing the services in the back of the lot and the facades on the streets witch mark their presence and automatically defines their lot. The lots are usually sizes that people can protect if the army came to tear the houses down; this dimension ends up being around 5mx10m. Each block is usually composed of entire families or at least people from the same original area or neighborhood. That said, social networks play a key role in the development and survival of these settlements. Moreover, we can begin to assume that different sectors or informal settlements come from different cultural and geographical backgrounds and as such, establish different types of values, skills, markets, etc.
In contrast, the Northwest part of the city grew around industries and was established as a blue-collar area. In this part of town, large factories would construct, adjacent to their main buildings, houses for their workers.
Around the 1970s, a “value-based mechanism” was established, where any infrastructure developments would be paid, in proportion to their adjacency and the increase in land value, by the surrounding areas. As the north consisted mostly of invasions and “blue-collar towns”, most likely unable to pay for any type of development, the city began to expand to the South, where most of the wealth was located. These areas are now called el Poblado,and Guayabal (the adjacent cities of Itagui and Envigado are now quickly developing as well).
What we now see in the city, is a high density accommodated by high-rises and open space in the south, and a very horizontal high density with barely any open space in the Northeast.