Mott Brooshovft Schmidt was born in Middletown, New York, on September 2, 1889. A fourth-generation American of German and Irish ancestry, he was one of three children born to Frances Jennette (1864-1940), third wife of Edward Mott Schmidt (1837-1910). After emigrating from Prussia in the early 19th century, the Schmidt family landed first in Charleston, South Carolina, settling some years later in New York. The first family member for whom we have records is Schmidt's great-grandfather, the physician John William Schmidt (1768-1853). His son, John W. Schmidt, Jr. (1811-1858), followed his father in medicine. He became the first visiting surgeon at St. Vincent's hospital, was a founding member of the New York Academy of Medicine and had a flourishing practice on 12th Street in Manhattan. Another member of the Academy was Valentine Mott (1785-1865), one of the fathers of modern vascular surgery and a professor at Columbia University. He was a friend of the Schmidt family. Mott Schmidt's unusual first name derives from this famous name in the annals of American medicine.
Schmidt's father was a veteran of the United States Army. His draft records indicate that he was a salesman before enlisting at the age of 37, in 1875, serving for 5 years. It is said that he had artistic inclinations, but no occupation is listed for him in the 1900 Census. The Schmidt family lived on a gentleman's income, and Mott attended public schools in Brooklyn with his brother (Girard b. 1891) and sister (Gladys b.1894). He grew up in a bourgeois environment, in a brownstone at 671 Park Place, near Prospect Park and Grand Army Plaza. His family was one of many to flock to the boroughs surrounding crowded Manhattan during the latter half of the nineteenth century. Brooklyn's cheaper and more spacious houses and other suburban advantages caused the city to grow from half a million to 806,343 residents between 1880 and 1890 alone. As a boy, Schmidt saw a city blossom around him, filled with handsome townhouses on neat tree-lined streets, so it is no surprise to find that he decided on a career in architecture at a very early age. He boasted that from age 9 he knew that he was to become an architect.
From 1904 to 1906 he attended Pratt Institute of Technology on nearby Willoughby Avenue, graduating with a Certificate in Architecture at the age of only 17. Although Pratt Institute (founded in 1887) was then mainly a trade and industrial design school, Schmidt took an interest in the Beaux Arts method of architecture which was being taught at most of the leading architectural schools. Like other Beaux Arts followers, Schmidt went on a two-year Grand Tour of Europe after completing his studies, visiting the continent's great monuments and producing skillful travel sketches in soft pencil. He was a talented draftsman and renderer, as his early drawings confirm, and this technique served him well in his later work. A portrait of him as a young man by Albert Sterner (1922) shows a handsome, sensitive face with delicate features and penetrating eyes.