John P. B. Sinkler was born in Philadelphia, the son of Dr. Wharton S. and Ella (Brock) Sinkler. His father was a neurologist and a trustee of the University of Pennsylvania. Young Sinkler attended the Episcopal Academy and Delancey School for his early education, and received his B.S. in Architecture from the University of Pennsylvania in l898. During the following year he attended classes at the Pennsylvania Academy of the Fine Arts but went on to Paris, where he attended the Ecole des Beaux-Arts. By 1902 he had begun some independent projects, but must have had a relationship with Perot & Bissell
because in 1904 when that partnership dissolved, the Philadelphia Real Estate Record and Builders Guide
announced that Perot, Bissell and Sinkler would all be opening individual offices in the Bailey Building at 1220 Chestnut Street. By 1906 he and E. Perot Bissell
had opened a new office under the name Bissell & Sinkler
. This relationship endured for approximately 30 years and was punctuated by several years of employment on Sinkler's part with the City of Philadelphia as City Architect.
Sinkler's term as City Architect from 1920 to 1924 was controversial due to the policy that the City Architect and a few draftsman would design most of the municipal buildings needed by the City, inevitably creating a vast backlog. Bandstands, such as the one which stood on the northeast corner of l5th and Arch, as well as bridges, park shelters, firehouses, and recreation buildings, required by the city's growth and the burgeoning park movement, were all designed by Sinkler and his small band of draftsmen. Perhaps his most noteworthy project during this time was the Germantown Town Hall of 1922, a replica of William Strickland's Merchants Exchange Building. By 1924 Sinkler had resigned from the position, advocating a reorganization of the department which would allow the City Architect to choose other architects in the city to handle the many necessary designs. His successor to the position, John Molitor, did direct work to practicing architects in the city; but Molitor was followed by William Covell, who returned to sole design responsibility for most of the city's buildings during his term. By 1932 a City Bureau of Architecture had been established, and Sinkler was asked to return as its Director. He filled this position for four years, concurrently serving on the City's Zoning Board of Adjustment and attempting to deal with the growth of tall office buildings in the City.
Sinkler's interest in historic buildings led him to participate in early restoration efforts of Independence Hall, and later he served as Trustee of the Naomi Wood Estate for Woodford Mansion in Fairmount Park. He also restored The Highlands, the estate of Caroline Sinkler in Ambler, PA.
Sinkler was active in both the T-Square Club and the American Institute of Architects. He joined the T-Square Club in 1898 and later served on its house, entertainment, and executive committees. He became a member of the AIA in 1906 and was elected a fellow in 1918. He served on the house committee and as chapter representative from 1916 to 1917; on the public works committee from 1919 to 1922; the architectural relations committee from 1925/26;and as Mid-Atlantic representative on the honor awards committee during 1928/29. He also served as president of the Philadelphia Chapter of the AIA. In addition, Sinkler held memberships in the University Barge Club, the Franklin Institute, and, during his university days, the Architectural Society of the University of Pennsylvania.