In 50 AD, the Romans founded Colonia Claudia Ara Agrippinensium (Cologne) on the river Rhine and the city became the provincial capital of Germania Inferior in 85 AD and one of the most important trade and production centers in the Roman Empire until it was occupied by the Franks in 462.
By the end of the 12th century, the Archbishop of Cologne was one of the seven electors of the Holy Roman Emperor. In 1288, Cologne gained its independence from the archbishops and became a Free City within the Holy Roman Empire. The Free Imperial City of Cologne must not be confused with the Electorate of Cologne which was a state of its own within the Holy Roman Empire.
Cologne's location at the intersection of the major trade routes between east and west as well as the south-north was the basis of Cologne's growth. By 1300 the city population exceeded 50,000.
Cologne lost its status as a free city when all the territories of the Holy Roman Empire on the left bank of the Rhine were incorporated into the French Republic and Napoleon's Empire.
The Cologne Cathedral, started in 1248, abandoned in 1560, was eventually finished in 1880 not just as a place of worship but also as a German national monument celebrating the newly founded German empire and the continuity of the German nation since the Middle Ages.
By World War I, Cologne had grown to 700,000 inhabitants. During World War II, the Allies dropped 44,923 tons of bombs on the city, destroying 61% of buildings, causing 20,000 civilian casualties and wiped out the central part of the city. In 1945 architect and urban planner Rudolf Schwarz called Cologne the "world's greatest heap of rubble". The reconstruction lasted until the 1990s.