Starting in 1852, Kapp worked as a journalist for the newly founded "Atlantic Studies". Their aim was to correct overly enthusiastic reports on the U.S. being circulated in Germany and also to show the darker side of American reality. Having become an American citizen in 1855, he was a lawyer until 1870 and worked as a foreign correspondent for the "Kölnische Zeitung", a newspaper in Cologne, Germany. He also wrote for the early numbers of the "Nation" of New York. From 1855, he was co-publisher of the "New Yorker Abend-Zeitung", a German newspaper in New York, and wrote several books about this flourishing country and the life of Germans in the United States. In politics, he associated with the Whigs.