Beyond the environs of Philadelphia, Mantle Fielding is probably better known as the compiler of an important source of biographical information regarding American artists as his Dictionary of American Painters, Sculptors and Engravers
, first published in 1926, has gone into multiple revised editions. However, Fielding did not intend to become an art historian; and his contributions to architecture, which were not limited to the Philadelphia area, are equally important in the understanding of his career. Fielding was born in New York City, the son of Mantle and Anna M. (Stone) Fielding. He graduated from Germantown Academy in 1883 and studied architecture for one year at MIT. By 1886 he is listing himself as an architect in the Philadelphia city directories, but he omits an office address from the listing, probably indicating that he was working in the office of another, more established, architect. In 1887 Fielding appears as a draftsman in the city directory, but in 1889 he launches an independent office (with an address at 110 South 4th Street), which he would continue to operate at least through 1938. Most of Fielding's work concentrated on residential design, and he particularly used the colonial revival style which emphasized the Pennsylvania farmhouse type.
Fielding joined the T-Square Club in 1886.