The ERA team started as a group of scientists and engineers working for the US Navy Communications Supplementary Activity - Washington (CSAW) during WWII on code-breaking. After the war set up their own company under the direction of William Norris in a disused St. Paul, Minnesota glider factory. They were dedicated to the construction of machines for use in scientific fields, designing and building a drum memory based machine called the Atlas computer in 1950. Atlas, built for the Navy, which was the first stored program computer in the US. The Atlas was later renamed the ERA 1101 for commercial sales (it was designed under "Task 13" and 1101 is binary for the decimal number 13).
Even before delivery of the Atlas, the Navy CSAW asked for a more powerful machine using both Williams tubes and drum memory, a machine known as the Atlas II computer. Work began in 1950 and the completed Atlas II was delivered to the NSA in September 1953. ERA looked to selling similar machines to a number of customers, but at about this time they became embroiled in a lengthy series of political manuverings in Washington that left them drained. In 1952 they were purchased by Remington Rand, largely as a result of these problems.
Remington Rand already had a computing division however, after they had purchased the Eckert-Mauchly Computer Corporation in 1950. For a time the two companies operated as independent units within Remington, with ERA focussing on scientific and military customers, while Eckert-Mauchly's UNIVACss were sold to business customers.
However in 1955 Remington merged with Sperry Corporation to become Sperry Rand. Both ERA and Eckert-Mauchly were folded into a single division as Sperry-Univac. Much of ERA's work was dropped while their drum technology was used in newer Univac machines. A number of employees were not happy with this move and decamped to form Control Data Corporation under the leadership of Norris.
But the core of the ERA team lived on. Eventually they were moved to a new research division where they had considerably more freedom. They worked primarily on computing systems for military use, and they pioneered a number of early command and control and guidance systems for ICBMs and satellites. There they were known as the Military Division, which was later renamed the Aerospace Division.
In the late 1970s, a number of Rand employees purchased the ERA name and started a small government contracting firm. In 1989, the "new" ERA became a wholly-owned subsidiary of E-Systems. In 1995, it was merged into the Melpar division of its parent and the name once again disappeared.