By about 1240 Bristol was finding it hard to accommodate the vast amount of trading ships in the busy port so it was decided the harbour had to be made larger. Labourers and stone masons dug a brand new channel out of the marshy land, to join the river Frome to the river Avon further downstream. This ultimately doubled the amount of mooring space available for ships. The new channel was known as the quay and still remains although much is covered by the city centre.

The thirteen hundreds brought misery and pain to Bristolians, like the rest of Asia and Europe. It was at this time many suffered from the devastating Black death which is said to have halved the population. It originated in Asia and spread overseas, most likely being brought into Britain through one of the major ports. People would cough up black blood and bile and many developed painful swellings in their armpits, neck and groin. The deaths were long and painful. The town of Gloucester kept Bristolians out, for fear of catching and spreading the disease. But despite their best efforts the disease hit them too, and although it eventually ceased many outbreaks occurred for centuries after. Such devastations like the black death were the result of unhygienic ways of living, the raw sewage and waste thrown into the rivers for example. And even though fresh water was supplied in the form of springs, it was expensive. Most of the drinking water could be considered poor quality, so most people drank beer instead. It was at the time a lot more hygienic and a way of avoiding other nasty waterbourne diseases like polio.

In 1497 John Cabot made his famous voyage on The Matthew where he discovered North America or 'new founde landes'. Initially the explorer set out to find a shorter route to Asia. It is thought that he sailed down the Bristol Channel, over to Ireland where he turned north to travel along the west coast of Ireland then out to sea. He departed Bristol in May of that year with about 20 crew aboard. It is estimated that after about 35 days at sea, John Cabot's men spotted land. He explored the region for around a month and returned to Bristol on the 6th August 1497. 14th century Bristol was flourishing and became the main point of departure for voyages to the new world. Ships would export wool and leather, and import wine, tobacco and cocoa beans. These imports became the basis of Bristol's manufacturing industries. It still wasn't until 1542, that Bristol was made into a city. James Millard, possibly a cloth merchant in the 1670s drew the first detailed scale map of Bristol and illustrated it with important buildings. This was the basis for updated versions which came later.

City of Bristol in the 1600's, had the advantage of not smelling as bad as other towns. By this time people were using cest-pits in their back gardens and a system of stone lined sewage pipes which carried sewage further down the Avon.

Also around this time, the biggest fear to Bristol merchants would be the Barbary pirates who were based on Lundy Island. Lundy Island in the Bristol channel was the perfect place for pirates, who could wait for merchant ships to sail out of the channel to steal their cargo, or even come in and raid the towns and villages on the channel itself.