During the 19th century Joensuu was a city of manufacture and commerce. Starting in 1860 local sawmills started to grow and prosper as the city received commercial rights and restrictions against industrial activities were lifted. An important centre of the glass industry developed in Utra – it had a considerable foreign population of about 11%. There was even a Swedish language school in those days.

Water traffic improved with the building of the Saimaa Canal in 1856. This made possible lively trade between the regions of North Karelia, St. Petersburg and Central Europe. At the beginning of the 20th century Joensuu was one of the largest port cities in Finland.

The River Pielisjoki has always been the lively heart of Joensuu. Throughout the centuries Karelian traders have travelled along the river and the canals which were completed at the end of 1870 and increased river traffic. Thousands of steamboats, barges and logging boats sailed along the river during this golden age of river traffic. The Pielisjoki has also been an important route for log-floating and has provided wood to the sawmills and the entire lumber industry.

In recent decades, the small agrarian town has developed into the vital centre of the North Karelia region. Joensuu had a population of 24 000 in 1954. Since 1960 economic growth in Finland has been strong and the decade saw the beginning of the urbanization process. In the 1960s the population of North Karelia decreased by more than 8% while the population of Joensuu grew by 28%. In 1960, the administrative region of North Karelia was also established and Joensuu became the capital of the region. In the 1970s, the kindergarten and comprehensive school systems were created, and many improvements were made in the field of social benefits.

The establishment of the University of Joensuu (now University of Eastern Finland) in 1969 and the further growth of the university have been crucial to the development of the city. Currently, the university comprises six faculties and nine independent units – and has close to 8000 full-time students. The university's diversified international cooperation in science, industry and commerce benefits the whole region.

The proximity of the eastern border has been an important factor throughout the history of the city. The Republic of Karelia in Russia has become - once again - a significant area for cross-border cooperation. The border station Värtsilä – Niirala is about an hour's drive from Joensuu. It was opened in 1991, and nowadays 1.5 million people cross the border annually. Export companies in Joensuu continue the traditions of past centuries in foreign trade. Cultural life also flourishes and gains new influences and reflections from the cultural diversity around the border.