Joseph D'Anna, opened the first MARS store on Old Eastern Avenue in Essex in 1943. The store was located at the center of an apartment and military housing community known as Mars Estates. Because of that location, Joe adopted the "Mars" name. Just down the road, Glenn L. Martin had developed and was building an aircraft that could take off from and land in water, the Mars Flying Boat. There is little doubt that the publicity surrounding this plane helped establish the Mars name in Eastern Baltimore County.

Together with a partner, Bob Daum, Joe owned and operated that small grocery store for three years. In 1945, Joe opened a second store in the 200 block of Eastern Avenue. In the same year, his two younger brothers returned from the war, first Carmen, who served in the Navy in the Pacific and then Angelo from the Army in Europe. Both brothers went to work with Joe and were made partners. One year later in 1946, Mars Super Market moved to Dundalk, closing the two locations in Essex. The partners leased a single unit in a new building, one containing seven store fronts and built by Charles Catalano and Sons.

Not long after the move, Angelo and Carmen bought the half of the business owned by Joe's original partner. Joe sold his interest in the business as well, leaving Carmen and Angelo each with a 50% share. Mars, as it now exists, started at that time even though the name preexisted the partnership. From that beginning, Angelo and Carmen promised to provide "only the best": the best meats, the best produce and the best and friendliest service. That has been the guiding philosophy over the years.

As business increased, the store was enlarged several times until it occupied most of the space on the southeast corner of Holabird and Delvale Avenues. A second store was needed, so Angelo and Carmen opened the Grey Manor store on Old North Point Road in 1954, followed only four years later by the Middle River store on Eastern Avenue (not far from Joe's original Mars). The company continued to grow due to the very positive response to their marketing approach. With the help of Morris Denkin, the company purchased the Vesper Family property on the opposite side of Holabird Avenue. With the on site direction of Carmen and Angelo, they constructed what many considered the most modern supermarket in the state of Maryland.

Anthony D'Anna, the youngest brother, came to work for Angelo and Carmen in 1949. Initially, he was a grocery and produce clerk, and later managed the store until he moved to a position in the office in 1963. He became Vice President and Senior Grocery Buyer.

After the company incorporated, Vincenzo F. D'Anna, their father, was elected to the board of directors as Chairman. In 1955, Anthony was made a partner and owner in the business.

After leaving the grocery business, Joe took over the operation of a restaurant from another younger brother, Vince D'Anna. Vince would later join the supermarket business, managing the new store on Eastern Avenue and buying produce for all the stores. Carmen brought Peter, the oldest brother, onboard as the company's Produce Buyer and Supervisor.