r/Glasgow Tools

u/Dunk546 gives the best explanation.

Glasgow was a very late bloomer and always quite a small provincial town, right up to the early modern period of the 1500s when it started to grow due to maritime commerce on the Atlantic. It went through a rapid growth spurt, such that even in the 1700s - 1800s, most of the city would have been relatively new.

The original medieval outline of the town was basically built around the four streets radiating out from Glasgow Cross (where the clock tower is today), but didn't extend much beyond that. The High Street leading north up the hill to the Cathedral and Bishop's Castle (the few wealthier folk around lived at the top of the hill, as tends to happen). The Saltmarket leading south towards the river. And Trongate leading west and Gallowgate leading east. Over time some other streets grew as stubs of these major artery streets, but that was generally it for the longest time. Much of this was built upon and replaced over centuries to the point that very little actual medeival stuff remained by the time the Victorians came along and carved out chunks of the old town for large warehouses and sandstone tenement dwellings.

In the Georgian era, with the growth of Atlantic trade, Glasgow grew insanely quickly, to the extent that much of the rest of the town has a very Georgian character. You can see this on streets like Bath Street, which still has most of its Georgian townhouses preserved, and in buildings like at Royal Exchange Square and GOMA, both of which were mansion houses belonging to wealthy Caribbean tobacco plantation owners and shipping magnates.

The Victorians replaced much of this, as well as the pre-existing old town core of Glasgow in the mid to late 1800s as the city went through another economic boom and insane growth in population (driven by steelworks, manufacturing and shipbuilding). The conditions of what might've otherwise been termed our "old town" we're so bad that it was cleared and replaced by tenement structures we largely still see there today, around Trongate, the eastern end of Merchant City, Gallowgate, along Saltmarket and up High Street. These photos by Thomas Annan capture what the old city core looked like at that stage - a hodgepodge of old pre-Georgian dwellings and early Georgian era tenements, a little like Edinburgh's old town looks today: https://digital.nls.uk/learning/thomas-annan-glasgow/explore/page-1/

Some of these were in then demolished in turn just a few decades later, around 1900, to make way for various things like railway lines and most obviously, the high street rail goods yard (which also involved the demolition and relocation of the original Glasgow University to the west end).

This website is a good place to start if you want to learn more about Glasgow history: https://www.theglasgowstory.com/story/?id=TGSD0