The brothers reached New York City by ship and went to Cincinnati where Mohr worked for a while in a German chemical company. On 3 March 1849, hit with gold fever, he set out with a group of 50 men for the gold mines of California, where they searched for gold on the slopes of the Sierra Nevada (US) in the Yuba Valley. The strenuous work of a gold miner and the continuous standing in cold water worsened his health. So, in December 1850, he traveled back to Cincinnati. On this trip, he met Duke Paul Wilhelm of Württemberg, who was returning from an expedition.