The Brooklyn Navy Yard in the foreground with the skyline of Lower Manhattan behind it. The 300-acre Navy Yard officially opened in 1806. Ohio, the first ship of the line built at the Navy Yard, was launched in May 1820. Working 24 hours a day, 70,000 people were employed at the Navy Yard during World War II, manufacturing ships. Today, around 7,000 people work at the Navy Yard in a variety of small businesses.