Inventor, Engineer. He is remembered best for designing the steam locomotive Novelty (in partnership with engineer John Braithwaite) and the ironclad ship USS Monitor that was used by the North during the American Civil War. Although none of his inventions created any large industries, he is regarded as one of the most influential mechanical engineers ever. Born and raised in Sweden, his father was a mine supervisor who moved his family to Forsvik, Sweden in 1810 when he lost money in speculations, and there he was in charge of blastings during the excavation of the Göta Canal. At age 14, he was already working independently as a surveyor. Three years later he joined the Swedish army and served in the Jämtland Field Ranger Regiment as a 2nd Lieutenant, but was soon promoted to 1st Lieutenant. He was sent to northern Sweden to do surveying, and in his spare time he constructed a heat engine which used the fumes from the fire instead of steam as a propellant. His skill and interest in mechanics made him resign from the army and move to England in 1826. His heat engine was not a success, as his prototype was designed to burn birch wood and would not work well with coal, the main fuel used in England. He invented several other mechanisms instead based on steam, and in 1829 he and John Braithwaite built the steam locomotive Novelty for the Rainhill Trials arranged by the Liverpool and Manchester Railway. It proved considerably faster than the other entrants but suffered recurring boiler problems, and the competition was ultimately won by English engineers George and Robert Stephenson with Rocket. He and Braithwaite constructed subsequent locomotives named William IV and Queen Adelaide after the new English king and queen but were unsuccessful in selling the new designs to the Railway. However, it proved to be an outstanding technical success by helping to quell the memorable Argyll Rooms fire on February 5, 1830. At this stage of his career, most successful and enduring of his inventions was the steam condenser, which allowed a steamer to produce fresh water for its boilers while at sea. Also, his "deep sea lead," a pressure-activated fathometer was another minor, but enduring success. The commercial failure and development costs of some of the machines he devised and built during this period put him into debtors' prison for a while. He then improved the ship design with two screw-propellers moving in different directions, as opposed to earlier tests with this technology, which used a single screw. However, the British Admiralty disapproved of the invention, which led to the fortunate contact with the encouraging American captain Robert Stockton who had him design a propeller steamer and invited him to bring his invention to the US. After moving to New York City, New York in 1839, Stockton's plan was for him to oversee the development of a new class of frigate with Stockton using his considerable political connections to grease the wheels. Finally, after the succession to the US Presidency by John Tyler, funds were allocated for a new design. Unfortunately they only received funding for a 700-ton sloop instead of a frigate. The ship, USS Princeton, took about three years to complete and was perhaps the most advanced warship of its time. In addition to twin screw propellers, it was originally designed to mount a 12-inch muzzle loading gun on a revolving pedestal, along with a collapsible funnel and an improved recoil system. His relationship with Stockton grew tense over time and, approaching the completion of the ship, Stockton began working to force him out of the project and carefully avoided letting outsiders know that Ericsson was the primary inventor. Stockton attempted to claim as much credit for himself as possible, even designing a second 12 inch gun to be mounted on the Princeton, which proved to be fatally flawed. When launched, Princeton was an enormous success. On October 20, 1843, she won a speed trial against the paddle steamer SS Great Western, until then considered the fastest steamer afloat. Unfortunately, during a firing demonstration of Stockton's gun, the breech ruptured, killing Secretary of State Abel P. Upshur and Secretary of the Navy Thomas Gilmer, as well as six others. Stockton attempted to deflect the blame onto Ericsson, with moderate success, despite the fact Ericsson's gun was sound and it was Stockton's gun that had failed. Stockton also refused to pay Ericsson, and by using his political connections, Stockton blocked the Navy from paying him. These actions led to Ericsson's later deep resentment toward the US Navy. In September 1854 he presented Napoleon III of France with drawings of iron-clad armored battle ships with a dome-shaped gun tower, and even though the French emperor praised this invention, he did nothing to bring it to practical application. Soon after the American Civil War broke out in 1861, the Confederacy began constructing an ironclad ram upon the hull of USS Merrimack which had been partially burned and then sunken by Federal troops before it was captured by forces loyal to the Commonwealth of Virginia. About the same time, the US Congress had recommended in August 1861 that armored ships be built for the American Navy. Although he still had a dislike for the US Navy, he was convinced by President Abraham Lincoln's hard-working Secretary of the Navy Gideon Welles, and shipbuilder Cornelius Scranton Bushnell to submit an ironclad ship design to them. He later presented drawings of USS Monitor, a novel design of armored ship which included a rotating turret housing a pair of large cannons. Despite controversy over the unique design, the keel was eventually laid down and the ironclad was launched on March 6, 1862, going from plans to launch in approximately 100 days. Two days later, the former USS Merrimack, rechristened CSS Virginia, was wreaking havoc on the wooden Union Blockading Squadron in Virginia, sinking the USS Congress and USS Cumberland. The Monitor appeared the next day, initiating the first battle (known as the Battle of Hampton Roads) between ironclad warships on March 9, 1862 at Hampton Roads, Virginia. The battle ended in a tactical stalemate between the two ironclad warships, neither of which appeared capable of sinking the other, but it strategically saved the remaining Union fleet from defeat. After the Civil War, he designed other naval vessels and weapons, including a torpedo boat that could fire a cannon from an underwater port. He also provided some technical support for John Philip Holland in his early submarine experiments. In the book "Contributions to the Centennial Exhibition" (1877, reprinted 1976) he presented his "sun engines," which collected solar heat for a hot air engine. One of these designs earned him additional income after being converted to work as a methane gas engine. He died at the age of 85, on the anniversary of the famous Battle of Hampton Roads of which his famous Monitor played a central role. He was initially interred at New York City's Marble Cemetery but was later moved to the Östra kyrkogården (East Cemetery) in Filipstad, Varmlands Lan, Sweden. For his endeavors, he was made a foreign member of the Royal Swedish Academy of Sciences in 1850 (Swedish member in 1863), a member of the Royal Swedish Academy of War Sciences in 1852, and an Honorary Doctorate Degree at Lund University, Lund, Sweden in 1868. Several monuments have been erected in his honor, including the John Ericsson National Memorial on The Mall in Washington DC, the John Ericsson Room at the American Swedish Historical Museum in Chicago, Battery Park in New York City, and the John Ericsson fountain at Fairmount Park, Philadelphia, Pennsylvania.