At age 26, Burnham moved on to the Chicago offices of Carter, Drake and Wight, where he met future business partner John Wellborn Root, who was 21, four years younger than Burnham.
The two became friends and then opened an architectural office together in 1873.
Unlike his previous ventures, Burnham stuck to this one.
Burnham and Root went on to become a very successful firm.
Their first major commission came from John B. Sherman, the superintendent of the massive Union Stock Yards in Chicago, which provided the liveliehood – directly or indirectly – for one-fifth of the city's population.
Sherman hired the firm to build for him a mansion on Prairie Avenue at Twenty-first Street among the mansions of Chicago's other merchant barons.
Root made the initial design.
Burnham refined it and supervised the construction.
It was on the construction site that he met Sherman's daughter, Margaret, whom Burnham would marry in 1876 after a short courtship.
Sherman would commission other projects from Burnham and Root, including the Stone Gate, an entry portal to the stockyards, which became a Chicago landmark.

In 1881, the firm was commissioned to build the Montauk Building, which would be the tallest building in Chicago at the time.
To solve the problem of the city's water-saturated sandy soil and bedrock 125 feet (38 m) below the surface, Root came up with a plan to dig down to a "hardpan" layer of clay on which was laid a 2-foot (0.61 m) thick pad of concrete overlaid with steel rails placed at right-angles to form a lattice "grill", which was then filled with Portland cement.
This "floating foundation" was, in effect, artificially-created bedrock on which the building could be constructed.
The completed building was so tall compared to existing buildings that it defied easy description, and the name "skyscraper" was coined to describe it.
Thomas Talmadge, an architect and architectural critic, said of the building, "What Chartres was to the Gothic cathedral, the Montauk Block was to the high commercial building."

Burnham and Root went on to build more of the first American skyscrapers, such as the Masonic Temple Building in Chicago.
Measuring 21 stories and 302 feet, the temple held claims as the tallest building of its time, but was torn down in 1939.

The talents of the two partners were complementary.
Both men were artists and gifted architects, but Root had a knack for conceiving elegant designs and was able to see almost at once the totality of the necessary structure.
Burnham, on the other hand, excelled at bringing in clients and supervising the building of Root's designs.
They each appreciated the value of the other to the firm.
Burnham also took steps to ensure their employees were happy: he installed a gym in the office, gave fencing lessons and let employees play handball at lunch time.
Root, a pianist and organist, gave piano recitals in the office on a rented piano.
Paul Starrett, who joined the office in 1888, said "The office was full of a rush of work, but the spirit of the place was delightfully free and easy and human in comparison to other offices I had worked in."

Although the firm was extremely successful, there were several notable setbacks.
One of their designs, the Grannis Block, in which their office was located, burned down in 1885, necessitating a move to the top floor of The Rookery, another of their designs.
Then, in 1888, a Kansas City, Missouri, hotel they had designed collapsed during construction, killing one man and injuring several others.
At the coroner's inquest, the building's design came in for criticism.
The negative publicity shook and depressed Burnham.
Then in a further setback, Burnham and Root also failed to win the commission for design of the giant Auditorium Building, which went instead to their rivals, Adler & Sullivan.

On January 15, 1891, while the firm was deep in meetings for the design of 
the World's Columbian Exposition, Root died after a three-day course of pneumonia.
As Root had been only 41 years old, his death stunned both Burnham and Chicago society.
After Root's death, t
At age 26, Burnham moved on to the Chicago offices of Carter, Drake and Wight, where he met future business partner John Wellborn Root, who was 21, four years younger than Burnham. The two became friends and then opened an architectural office together in 1873. Unlike his previous ventures, Burnham stuck to this one. Burnham and Root went on to become a very successful firm. Their first major commission came from John B. Sherman, the superintendent of the massive Union Stock Yards in Chicago, which provided the liveliehood – directly or indirectly – for one-fifth of the city's population. Sherman hired the firm to build for him a mansion on Prairie Avenue at Twenty-first Street among the mansions of Chicago's other merchant barons. Root made the initial design. Burnham refined it and supervised the construction. It was on the construction site that he met Sherman's daughter, Margaret, whom Burnham would marry in 1876 after a short courtship. Sherman would commission other projects from Burnham and Root, including the Stone Gate, an entry portal to the stockyards, which became a Chicago landmark.
In 1881, the firm was commissioned to build the Montauk Building, which would be the tallest building in Chicago at the time. To solve the problem of the city's water-saturated sandy soil and bedrock 125 feet (38 m) below the surface, Root came up with a plan to dig down to a "hardpan" layer of clay on which was laid a 2-foot (0.61 m) thick pad of concrete overlaid with steel rails placed at right-angles to form a lattice "grill", which was then filled with Portland cement. This "floating foundation" was, in effect, artificially-created bedrock on which the building could be constructed. The completed building was so tall compared to existing buildings that it defied easy description, and the name "skyscraper" was coined to describe it. Thomas Talmadge, an architect and architectural critic, said of the building, "What Chartres was to the Gothic cathedral, the Montauk Block was to the high commercial building."
Burnham and Root went on to build more of the first American skyscrapers, such as the Masonic Temple Building in Chicago. Measuring 21 stories and 302 feet, the temple held claims as the tallest building of its time, but was torn down in 1939. 
The talents of the two partners were complementary. Both men were artists and gifted architects, but Root had a knack for conceiving elegant designs and was able to see almost at once the totality of the necessary structure. Burnham, on the other hand, excelled at bringing in clients and supervising the building of Root's designs. They each appreciated the value of the other to the firm. Burnham also took steps to ensure their employees were happy: he installed a gym in the office, gave fencing lessons and let employees play handball at lunch time. Root, a pianist and organist, gave piano recitals in the office on a rented piano. Paul Starrett, who joined the office in 1888, said "The office was full of a rush of work, but the spirit of the place was delightfully free and easy and human in comparison to other offices I had worked in."
Although the firm was extremely successful, there were several notable setbacks. One of their designs, the Grannis Block, in which their office was located, burned down in 1885, necessitating a move to the top floor of The Rookery, another of their designs. Then, in 1888, a Kansas City, Missouri, hotel they had designed collapsed during construction, killing one man and injuring several others. At the coroner's inquest, the building's design came in for criticism. The negative publicity shook and depressed Burnham. Then in a further setback, Burnham and Root also failed to win the commission for design of the giant Auditorium Building, which went instead to their rivals, Adler & Sullivan.
On January 15, 1891, while the firm was deep in meetings for the design of 
the World's Columbian Exposition, Root died after a three-day course of pneumonia. As Root had been only 41 years old, his death stunned both Burnham and Chicago society. After Root's death, t
Daniel Burnham