McDermott was born in South Boston, Massachusetts, on March 30, 1854, to a Scottish family.

[2] He worked as a newspaper reporter for several years, and then began to study law with Leon Abbett.

[6] He was a member of the New Jersey General Assembly in 1880 and 1881,[7] and served as a district court judge from 1883 to 1886.

[13] He was elected as a Democrat to the Fifty-sixth Congress to fill the vacancy caused by the death of William D.

[14] He was reelected to the Fifty-seventh, Fifty-eighth, and Fifty-ninth Congresses and served from December 3, 1900, to March 3, 1907.