Soulard was born in Rochefort, France in 1766. He followed in his father's footsteps and became an officer in the French Royal Navy, but was forced to leave France during the Revolution. By 1795 Soulard was living in St. Louis and was appointed the King's Surveyor General of Upper Louisiana.
In 1795 Soulard made an important map of the middle Mississippi and Missouri rivers, which was later copied and used by Lewis and Clark in 1804. On November 16, 1795, Soulard married Julie Cerre, daughter of St. Louis merchant Gabriel Cerre.
When the Americans arrived in St. Louis in 1804 they appointed Soulard surveyor general, but by1806 he was dismissed, primarily because he was too personally interested in the results of surveys due to land grants he had received. Soulard spent much of the rest of his life trying to regain title to lands granted to him by the Spanish crown.
He died in his home in St. Louis on March 10, 1825. His wife Julie continued to fight for the titles to their lands, and by 1836 had re-secured the deed to the area of St. Louis' Soulard Market. She died on May 9, 1845. A section of the modern City of St. Louis is named Soulard after Antoine and Julie Soulard.