Alternative Names:  Cosden Building
Address: 401-409 South Boston Avenue
Height: 513.01
Floors: 36
Constructed: 1918

Located at 401 South Boston Avenue in downtown, Tulsa, Mid-Continent Tower is the fourth-tallest building in Tulsa and fifth-tallest in the State of Oklahoma.

Known for its distinctive green copper roof (copper that is exposed to the elements undergoes a series of chemical reactions that give the metal a pale green outer layer called a patina), the building’s fascinating history spans nearly 70 years.

Little known to the public, is that Mid-Continent Tower is actually two separate structures. The first 16-story structure, which was built in 1918, was originally known as the Cosden building.

Corden Building, c.1920s

Josh Cosden (1881-1940) was a Maryland-born drugstore clerk-turned oil man who had built and lost two fortunes before coming to the region during the oil boom. In 1910, Cosden constructed an oil refinery in Bigheart, Oklahoma. After some success, he opened up a refinery in West Tulsa and consolidated his drilling, pipeline and refining operations, creating Cosden and Company in 1917.

It was during this time that the oil magnate built Tulsa’s first skyscraper, the Cosden Building on the former site of the first Tulsa schoolhouse, which was built in 1885 on Creek Indian Nation land.

According to the Tulsa Preservation Commission, the Cosden Building was one of the earliest reinforced concrete buildings in the United States.

“The basic design was Sullivanesque, but a Venetian Gothic terra cotta skin was applied to the building. The building was a gesture toward progressive design in a young city, and an interpretation of the “commercial cathedrals” of the age. The Cosden Building is the cornerstone of Boston Avenue’s older financial and corporate office buildings. This million-dollar building symbolized the flamboyance of Tulsa’s oil barons during a period of enormous growth and prosperity.”

Preservation and Conversion to Mid-Continent Tower

After decades of degradation and decay, and 62 years since its original construction, the Cosden Building was preserved and restored in 1980. Following the project to clean up the property, the location was given new life, when in 1984 a new 20-story tower was cantilevered over the top of it.

The building grew from 16 floors to 36 floors, with the latter 20 appearing to rest on top of the original structure. While Mid-Continent Tower looks like one building, the top 20 floors are independently supported by a steel addition built onto the east side of the older structure.

Staying true to the Cosden Building’s Sullivanesque, Neo-Gothic architecture, the addition seamlessly joined together two structures 66 years apart; forever altering the Tulsa skyline, while also preserving a priceless piece of Tulsa history.

The Building’s Copper Roof

The building’s copper roof, with its weathered patina, is a prominent feature of the downtown skyline. Copper goes through a natural oxidation process that forms a unique protective patina on the metal.

The surface of the metal undergoes a series of color changes — ranging from iridescent/salmon pinks, oranges and reds with brassy yellows, blues, greens and purples. As the oxide thickens, these colors are replaced by russet and chocolate browns, dull slate grays or blacks, and finally to a light-green or blue-green.

The entire process generally takes around one year, but has given Tulsans a unique landmark to be proud of for more than three decades.