Boston was without a true aquarium for nearly fifty years after the closing of the Boston Aquarial Gardens and Zoological Gardens and it was not until 1912 that the city undertook construction of a new aquarium.

In the late nineteenth century, the marsh flats in South Boston were an eyesore, disfigured with all manner of debris from the harbor. The city made the decision to create a recreational park by leveling a nearby hill and filling in the flats. From the outset an aquarium was envisioned as part of a new marine park. The Boston Society of Natural History, whose membership included the elite of local society, had an ambitious project for the proposed park. It would include two aquariums: a saltwater aquarium at Marine Park and a freshwater aquarium at Ward's Pond, north of Jamaica Pond. The freshwater aquarium was never built. The Society of Natural History wanted to emphasize the educational aspects of the new aquarium. The exhibits should manifest "the relation of animals and plants to their surroundings...the suitability of organisms to do the work they have to perform, illustrating this in many ways."

The filling of the marsh flats was completed in the 1890s. Castle Island was ceded to the City of Boston by the Federal government and a covered bridge was built between Marine Park and the island, later replaced by a causeway. A great pier was laid out on the other side of Marine Park including what is now known as Pleasure Bay. Three large ponds were left in the flats to be used for the new aquarium. It was proposed to use these flats for amphibious animals and marine mammals including porpoises, seals, and walruses. The work on the ponds was finished in 1893.

Unfortunately, once the filling in and beautification of Marine Park were completed, the city did not have sufficient funds to build the new aquarium. It was not until 1912 that the City of Boston undertook the construction of the aquarium thanks to a fund set up in the will of George F. Parkman for the improvement and maintenance of the city's parks. The aquarium was inaugurated on Thanksgiving Day, 1912.

The architect was William Downes Austin, the designer of the Detroit Aquarium. The original Boston project called for a much smaller building. The city fathers, however, not wanting to be outdone by Detroit, allotted the necessary funds to double the size and double the price. The total cost was $135,778.

Like most aquariums built at this time, the South Boston Aquarium resembled a church or museum, with the fish tanks presented like portraits on the walls. There was, however, an effort to exhibit the fish as they would appear in their natural habitats and an attempt was made to simulate caverns and grottos under the sea. The aquarium building was about 8000 square feet in size. It was L-shaped, with a dome and a large seal pool under the dome. The exterior was brick covered with roughcast plaster. The roof was of wood, covered with red shingle tiles. The dome was surmounted by a bronze weather vane in the form of a cod.

The entrance portal was elaborate. The entrance fetured woodcarvings of dolphins, crabs and other marine life. The interior floors and walls were of multicolored terrazzo. The recessed patio was of white marble with panels of colored marble. Two pillars, with capitals representing sea horses and shells, supported a marble arch with a keystone depicting Cupid riding a dolphin. At the base of the arches, on either side over the columns, were life-sized figures of mermaids riding the waves and combing their long tresses with coral.

The fifty-five exhibit tanks were built of cypress, each about five feet high and 3 1/2 feet deep. English plate glass was used for the tanks and for tank partitions. The tanks were about two feet above the main floor and were lighted by skylights during the day and by electric light diffused through the tanks in the evening. Salt water from the harbor was pumped into an underground reservoir with a capacity of 100,000 gallons. From there, it was pumped to distributing tanks in the attic and then sent by gravity to the exhibit tanks. One of the distributing tanks was fitted with a steam coil to warm the salt water for the tropical fishes. The seawater in the tanks was in constant circulation and was returned to the underground reservoir through filter beds.

The exhibits included several species of large turtles, local fresh- and saltwater fishes, tropical saltwater specimens and a number of seals. The South Boston Aquarium made no secret of its mandate. It was "primarily and principally for the exhibition of fishes and only very secondarily for the promotion of scientific study." No attempt was made to train the seals nor educate the public, yet the aquarium attracted as many as 15,000 visitors in a single day.

The aquarium depended on the Park Department of the City of Boston. The Franklin Park Zoo was developed at the same time as the aquarium and it also depended on the Parkman Trust for it’s funding. In the beginning, the zoo got more public attention than the aquarium.

Within two years of its inauguration, the South Boston Aquarium underwent a management crisis. Its first director was Louis Mowbray. He had dreams of making the South Boston Aquarium a first class institution and a model for scientific research. But to do so required money. In January of 1914, Mowbray was allotted $1,500, a large sum at the time, to purchase fishes in Philadelphia. A month later he was fired for "inefficiency and conduct injurious to the discipline of the Park Department." He did not dispute the injurious conduct charge but demanded that the accusation of "inefficiency" be struck from his record as unfounded and misleading. The Park Department complied with his request.

Louis Mowbray went on to become one of the most famous and respected ichthyologists of his time. He went from Boston to head the New York Aquarium for several years and was the director of a Miami aquarium until it was sold in 1924. After another short stay in New York, he returned to his native Bermuda, where he served as curator of the government aquarium until his death in 1952. He is credited with the discovery and capture of several species of rare fish.

At the time, Mowbray's vision was at odds with an aquarium was never designed for scientific research. The city had already spent twice as much as originally intended in the construction of the building and had been generous both in supporting his salary and plans for stocking the aquarium. There were not the means to satisfy his broader ambitions for the institution.

His successor was John Benson, who, from 1914 to 1919, managed both the Franklin Park Zoo and the South Boston Aquarium. To renew the exhibits of tropical fishes, collecting trips too place off Key West; the cold-water specimens were collected at Woods Hole. Benson took his responsibilities seriously, pushing for improvements in both the zoo and aquarium but eventually his efforts were rebuffed and in 1919 his position was abolished. There would be a Superintendent but no Director.

During the 1920s there was a sustained effort to replace corroded pipes, add new fixtures and exercise preventive maintenance. With the help of the Detroit Aquarium, fishes from the Great Lakes were added to the exhibits while the rest of the stock was renewed annually by buying into the Caribbean collecting trips of the New York Aquarium and expeditions to Woods Hole.

During the Great Depression and the Second World War, maintenance and replacement of defective fixtures practically ceased and only "survival maintenance" was undertaken between 1930 and 1946. The priorities of the city and country — and even the Park Department — were elsewhere. The annual renewal of exhibits continued during this period but with diminished funds. The final expedition to Woods Hole was allotted a paltry $39.00. No private benefactor stepped forward to take an interest in the Aquarium.

After the war, the underfunded and neglected aquarium was in a pitiful state. Almost half the tanks were empty, the water in the occupied tanks was murky, only one seal of the colony remained, and the building was in dire need of structural repair. At the time, it was estimated that the rehabilitation would require $300,000. Mayor Hynes refused to appropriate the money and ordered the building closed.

September 30th, 1954, was the South Boston Aquarium's last day. The remaining seal and fishes were sent to the Franklin Park Zoo. The five huge turtles, all over 200 pounds, the Aquarium’s sole remaining attraction, were sent away. Rumor has it that Myrtle, the New England Aquarium's famous giant green turtle, is one of these. It's not impossible; she came to the New England Aquarium from the old Provincetown Aquarium, and that would have been a logical place to send the Boston turtles.

A public tennis court now stands on the site of the South Boston Aquarium. An MDC skating rink has taken over the three ponds. Across the street Admiral Farragut still looks out on Boston Harbor. The willow tree is no longer there but the long blue waves still rise steadily beyond the outer islands.

The South Boston Aquarium was free, it was run by the City of Boston, it had no well articulated scientific ambitions nor educational programs. Its solvency depended on the local government, not on attendance. Its exhibits were modest. Yet, when it was properly maintained, it attracted up to half a million people yearly who simply came to see the fish and aquatic life.

The New England Aquarium timeline