After completion of his schooling, Ritter was introduced to Bethmann Hollweg, a banker in Frankfurt. It was arranged that Ritter should become tutor to Hollweg's children, but that in the meantime he should attend the University of Halle at his patron's expense. His duties as tutor began in 1798 and continued for fifteen years. The years 1814–1819, which he spent at Göttingen in order still to watch over his pupils, were those in which he began to exclusively study geography. It was there that he courted and married Lilli Kramer, from Duderstadt and that he wrote and published the first two volumes of his Erdkunde.

The first volume of Die Erdkunde was completed in Berlin in 1816, and a part of it was published in the following year. The whole of the first volume did not appear until 1832, and the following volumes were issued from the press in rapid succession. Die Erdkunde was left incomplete at the time of Ritter's death, covering only Asia and Africa.

In 1819 he became professor of history at Frankfurt, and in 1820 he received a teaching appointment in history at the University of Berlin. Ritter received his doctorate there in 1821, and was appointed professor extraordinarius in 1825. He also lectured at a nearby military college. He was particularly interested in the exploration of Africa and held constant contacts with British scholars and scientific circles like the Royal Geographical Society. He was one of the academic teachers of the Explorer Heinrich Barth, who traveled in Northern and Western Africa on behalf of the British government to negotiate treaties that were to stop the Trans-Saharan slave trade. Carl Ritter himself was a dedicated anti-slavery propagandist in Germany.

In 1822 Ritter was elected to the Prussian Academy of Sciences, and in 1824 he became a corresponding member of the Société Asiatique de Paris. In 1828, he established the Gesellschaft für Erdkunde zu Berlin (Berlin Geographical Society). He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1849. In 1856, he was appointed curator of the Royal Cartographic Institute of Prussia. He died in Berlin in 1859.

Many of Ritter's writings were printed in the Monatsberichte of the Berlin Geographical Society, and in the Zeitschrift für allgemeine Erdkunde. His Geschichte der Erdkunde und der Entdeckungen (1861), Allgemeine Erdkunde (1862), and Europa (1863) were published posthumously. Some of his works have been translated into English by W. L. Gage: Comparative Geography (1865), and The Comparative Geography of Palestine and the Sinaitic Peninsula (1866)

In 1865, a monument to Ritter was installed at the entrance to the Bruehl in Quedlinburg. The house where he was born, number 15 Steinbrücke, was torn down in 1955. There is an additional monument at the Mummental school honoring both Ritter and his Teacher Johann Christoph Friedrich GutsMuths. The Ritter Range in California is named after him.

Ritter's writings thus also had implications for political theory. His organic conception of the state could be abused to justify the pursuit of Lebensraum, even at the cost of another nation's existence, because conquest was seen as a biological necessity for a state’s growth. His ideas were adopted and transformed into an expansionist ideology by the German geostrategist Friedrich Ratzel. It is to be doubted, however, whether Carl Ritter can be held responsible for this interpretation, which was developed under the influence of Darwinism, which was to become a leading and popular ideology in Germany only after Ritter's death.