Clarence was born in Philadelphia, the son of Alfred Zantzinger (1839-1873) and Sarah Crawford Clark.

Alfred was a medical doctor who was born on June 27, 1839, in Philadelphia to George Zantzinger, a grand-nephew of David Rittenhouse,^[1] and Caroline Helmuth.^[2] Alfred entered the University of Pennsylvania in 1855, graduated from Philadelphia's Hahnemann Medical College in 1862,^[2] and became a volunteer surgeon with the First Troop Philadelphia City Cavalry.^[3] In January 1863, Alfred married Sarah Crawford Clark, the daughter of Philadelphia financier Enoch White Clark.^[2] When their son was born in 1872, they named him for Sarah's brother Clarence Clark.

Alfred died of typhoid in Philadelphia on August 15, 1873.^[4] Sarah later married C. George Currie, a rector of St. Luke's Church in Philadelphia.^[5]

Clarence attended private school in Germany, then St. Paul's School in Concord, New Hampshire. He matriculated at Yale University's Sheffield Scientific School, where he was a member of the senior S.S.S. Society^[6] and graduated with a degree in civil engineering in 1892. Three years later, he earned a B.S. in Architecture at the University of Pennsylvania. He then spent two years at the Ecole des Beaux-Arts in Paris, where he worked under Paul Blondel and Henri Grisors and graduated in 1901.^[7]

He returned to Philadelphia, set out his shingle, and soon received his first commission: a building to house the West Philadelphia branch (today, the Walnut Street West branch) of the Free Library of Philadelphia.^[8] By 1905, he and Charles L. Borie, Jr. (a fellow graduate of St. Paul's School) had launched a firm of their own with offices at 251 South 4th Street in Philadelphia. They were joined in 1910 by Milton Bennett Medary, and the firm was renamed Zantzinger, Borie & Medary, which specialized in institutional and civic projects.^[7]

In 1903, Zantzinger joined the American Institute of Architects; eight years later, the group made him a fellow. He served for years on the group's National Committee on Foreign Relations and Education; he also served as president of the Philadelphia chapter. Zantzinger was also a member of the T-Square Club; he directed its atelier and served on its education committee.^[7]

In 1906, he was elected to the board of directors of the Pennsylvania Academy of the Fine Arts.^[9]

In 1917, Zantzinger became a diplomat: President Woodrow Wilson appointed him to represent the U.S. on the War Trade Board in Sweden as a member of the U.S. legation in Stockholm.^[7]

He also served on the National Capital Parks and Planning Commission and as president of Philadelphia's City Parks Association.^[7]

In 1951, he retired from his firm, by then renamed Zantzinger & Borie.^[10]

Among his works were:^[10]

• William Penn Charter School, Germantown, Pennsylvania.
• Pennsylvania Athletic Club, Philadelphia.
• Bryn Mawr Hospital, Bryn Mawr, Pennsylvania
• The bank building of E.W. Clark & Co., southeast corner of S. 16th and Locust Streets in Philadelphia.^[11]
• St. Paul's Church, Chestnut Hill, Pennsylvania.
• Crescent Avenue Presbyterian Church, Plainfield, New Jersey.
• The administration building for the Sheffield Scientific School at Yale.
• The redevelopment of his uncle's estate in West Philadelphia for Philadelphia Divinity School; today, the public Penn Alexander elementary school^[12]
• The Men's dormitory group, University of Chicago.
• Department of Justice Building, Washington, D.C.
• Public Administration Building, University of Chicago.
• Graduate Cottage, Overbrook School for the Blind, Overbrook, Pennsylvania.
• Nurses Home, Abington Hospital, Abington, Pennsylvania.
• Warehouse for the Philadelphia Navy Yard.
• Private house, 8500 Seminole Avenue, Philadelphia^[13]

In 1903, Clarence married Margaret Shippen Buckley (d. Jan. 16, 1958^[14]),^[10] part of a prominent Philadelphia family that descended from John Buckley (1664-1732), of Wiltshire, England, who in 1681 became one of the first people to purchase land in the colony of Pennsylvania from William Penn.^[15] She was a daughter of iron manufacturer Edward Swift Buckley^[15] and granddaughter of Matthew Brooke Buckley (1794-1856),^[16] a president of the Philadelphia, Wilmington and Baltimore Railroad from 1842^[17] to 1846.^[18][19] Matthew was the son of Daniel Buckley (1761-1827), a lawyer and former member of the Assembly of Pennsylvania.^[20]

In 1922, Clarence and Margaret lived at "Greenacre", their house at Seminole and Highland Avenues in Chestnut Hill, Pennsylvania.^[21]

They had at least four children:

1 Clarence Clark Zantzinger Jr. (1904-1993), who followed his father to St. Paul's, Yale, Penn, and the Ecole des Beaux Arts; then joined Zantzinger, Borie & Medary as a draftsman; and finally struck out on his own as an architect. His firm, Kneedler, Mirick & Zantzinger, "designed office buildings, hospitals, churches, museums, schools and houses in the Philadelphia area," according to his New York Times obituary.^[22] He served as director or other corporate officer in several organizations, including the Fairmount Park Art Association, for which he served as president from 1969 to 1980.^[23] He married Mary Amory Cook, a daughter of Navy Vice Admiral Arthur Byron Cook (1881-1952), an early naval aviator.

2 Alfred Zantzinger (1907-1972), who also attended St. Paul's, married Mary Geist in 1937. Alfred worked stints at the E.W. Clark & Co. financial house, the Philadelphia Suburban Water Company, and as vice-president of the Pennsylvania Academy of the Fine Arts.^[24]

3 Sarah Clark Zantzinger married Harry C. Groome Jr.,^[25] who went on to become a senior vice-president of N. W. Ayer & Son, the country's oldest advertising agency.^[26]

4 Mary Vaux Zantzinger (1910-1987), who married John Wister Wurts (1907-1972).^[25] Wurts, who lived as a child on Philadelphia's Portico Row, graduated from Princeton University in 1931^[27] and served in Europe during World War II, winning the Legion of Merit.^[28]

• Portrait (c. 1945) of Clarence Clark Zantzinger by Alice Kent Stoddard (1883?-1976)
• Photo of "Kate's Hall" at 8440 St. Martins Lane in Chestnut Hill, designed by Zantzinger for Joseph Sill Clark, Sr.
• St. Paul's School obituary for Clarence Zantzinger
• Inquirer obituary for Clarence Jr.
• New York Times obituary for Clarence Jr.