Alexander Wadsworth Longfellow, Jr.

Alexander Wadsworth Longfellow Jr. (August 18, 1854, Portland, Maine – February 16, 1934, Portland) was an American architect and nephew of poet Henry Wadsworth Longfellow.

Alexander Wadsworth Longfellow Jr. was the son of Alexander Wadsworth Longfellow Sr. (1814-1901), a U.S. Coast Survey topographer, and of Elisabeth Porter. After graduating from Harvard University in 1876, he studied architecture at the Massachusetts Institute of Technology and the École des Beaux-Arts in Paris, then worked as senior draftsman in Henry Hobson Richardson's office.

After Richardson's death in 1886, Longfellow teamed up with Frank Ellis Alden (1859-1908) and Alfred Branch Harlow (1857-1927) to found the firm of Longfellow, Alden & Harlow, with offices in Boston and Pittsburgh. The firm designed the Carnegie Library of Pittsburgh, the City Hall in Cambridge, Massachusetts. They also designed the Arnold Arboretum headquarters, the Hunnewell Building, in 1892 which was constructed with funds donated by philanthropist-horticulturalist Horatio Hollis Hunnewell in 1903.