The Merchant City was formerly the residential district of the wealthy city merchants in the 18th and early 19th centuries, particularly the Tobacco Lords from whom many of the streets take their name. As the Industrial Revolution and the wealth it brought to the city resulted in the expansion of Glasgow’s central area westward, the original medieval centre was left behind. Glasgow Cross, situated at the junction of High Street, Gallowgate, Trongate and Saltmarket was the original centre of the city, symbolised by its Mercat cross. Glasgow Cross encompasses the Tolbooth Clock Tower; all that remains of the original City Chambers, which was destroyed by fire in 1926.
~the above from Wikipedia