Over the next twenty years, several buildings were constructed and the animal collection grew to include bears, elk, moose, hyenas, leopards and an elephant. During the Depression the WPA built several structures at the zoo including the bear dens, wolf pens, monkey islands and the elephant house. In 1946, a Himalayans Black Bear that was the mascot of the bomber unit in World War II’s Pacific Theater was donated to the zoo. This bear was quite a celebrity having accompanied crews on several bombing runs during the war.

The most famous zoo resident by far was Mr. Magoo, an Indian Mongoose that in 1963 was smuggled into the country by a merchant seaman. Due to a federal ban on mongoose in the country, the government ordered his destruction. The local public outcry spread to a nationwide issue that went to the highest levels of government. It ended with an official presidential pardon signed by President Kennedy that spared the life of Mr. Magoo. Needless to say, Mr. Magoo became a national celebrity. He remained at the zoo until his death in 1968. A popular book "The Duluth Mongoose" by Jack Denton Scott told the story of this famous animal.

Throughout the 1960’s and 70’s the zoo continued to grow, adding jaguars, cougars, crested porcupines, kangaroos, chimpanzees, reindeer and giant tortoises. While a new children’s zoo and an aviary were built, most of the animals were still found in old barred cages and cramped paddocks.

For many years the zoo management was appointed by the mayor and usually changed with each administration. For that reason the Arrowhead Zoological Society was formed, and in 1959, assumed management of the zoo. This arrangement stayed in place for about 30 years. Under the current management agreement, the Zoological Society is under contract with the City to operate admissions, concessions, and provide memberships, promotions, fund raising and education.

In 1987, $4 million was appropriated by the state legislature for zoo improvements. The City allocated approximately $3 million in additional funding. With this money, work on the Zoo Master Plan was begun. Improvements included new naturalistic exhibits for lions, bears, cougars, the Australian Connection, and Polar Shores, which features otters, seals, penguins and polar bears in exhibits with above and below water viewing.

In 1992, Phase II of the Master Plan was begun. It included the renovation of the old main building from row upon row of cramped cages for cats and primates into offices, a gift shop, restaurant and education areas. Also included were a two-story Macaque exhibit and a large deck overlooking a Siberian Tiger exhibit as well as providing a view of the entire zoo.

In 1993, the Lake Superior Zoo hosted the Midwest Regional AAZPA Conference.

In 1996, Phase III of the Master Plan was to be started with a $1.5 million grant from the State that was to be matched by $1.5 million from the City. These funds were approved by the House and Senate, but unfortunately were among the 30 or so projects vetoed by the governor.

Although this was certainly a setback and will delay some projects, funds will be found to complete the final phase of the Lake Superior Zoo. The zoo is an important part of the fabric of Duluth and it will continue to prosper.

In 2000, construction began on the new Willard Munger Animal Care Center. Now open, the care center provides for more than 450 animals in the zoo. The keepers and veterinary team are equipped with the finest facility possible.

             

Construction to the Griggs Learning Center also began. The Learning Center, located in the main building, houses all the education animals and provides space for education programs, along with hands-on opportunities for zoo visitors. In February 2001, the Griggs Learning Center Officially opened to the public.