Julius Erasmus Hilgard was born on January 7, 1825, in Zweibrücken, Bayern, Germany.

He was a German-American engineer and geodesist. In 1835, he arrived with his family in America. He was then taught at home by his father Theodor Erasmus Hilgard (1790-1873), a judge, until 1843, when he moved to Philadelphia, Pennsylvania, to study civil engineering. His first work was in the preliminary surveys of the Bear Mountain Railroad. Due to his abilities, he soon got a position in the U.S. Coast Survey, where he served, with short interruptions, until his death. In 1845, Hilgard began surveying coastline in the lower Chesapeake Bay, and between 1846 and 1850 he divided his time between taking part in surveys of the Mississippi Sound and the Florida Keys and making computations in the office. Throughout the American Civil War, he served the Union army and navy by the construction of maps and charts and by surveys as well as by tidal and other information. In 1863, he played a prominent role in organizing the National Academy of Sciences to advise the U.S. government on matters related to science and technology and became one of its first fifty members. He was elected as a member of the American Philosophical Society in 1863. From 1864 to 1867, he served as the U.S. Coast and Geodetic Survey’s Acting Superintendent. In 1872, he joined the International Metric Commission at Paris and was made a member of the permanent committee. In 1875, he was president of the American Association for the Advancement of Science.

In 1848. he married Catherine S. Clements (1828-1894). He died on May 8, 1891, in Washington, D.C., USA.