On March 14, 1899, U.S. Patent No. 621195 issued to Ferdinand Graf Zeppelin on a navigable balloon:

Ferdinand Graf Zeppeli was born July 8, 1838, he was a Count and general. He served as an official observer with the Union Army during the U.S Civil War, visiting the balloon camp of Thaddeus Lowe, and then made his first ascent in a balloon in St. Paul with former Army balloonist John Steiner, which was the inspiration of his later interest in aeronautics. Zeppelin’s ideas for large airships were first recorded in a March 25, 1874, diary entry.

After resigning from the Army in 1891, at the age of 52, Zeppelin devoted himself to designing an air ship. He patented the design in Germany in 1895 and in the United States in 1899. After initial succes, the name Zeppelin came to be commonly used to refer to all forms of rigid airships. Zeppelin also created the world’s first commercial airline, using his air ships.