William Lloyd Baily pursued two careers, combining his life as a successful architect with an active interest in ornithology which resulted in his acting as Inspector of Birds and Mammals at the Port of Philadelphia, a post which he held from 1900 until his death. Baily was born in Germantown and was the son of textile magnate Joshua L. Baily and wife Theodate. He attended Friends Select School in Germantown and went on to the William Penn Charter School, from which he graduated in June, 1880. From there he proceeded to Haverford College, where he took courses in perspective, mechanical and freehand drawing, survey, and sanitary engineering. Following his graduation from Haverford in 1883, he began a peripatetic office career, commencing with a one-year stint with Theophilus Parsons Chandler
. From 1884 to 1885 Baily worked in the office of Addison Hutton
; from 1885 to 1886 he worked successively for Frank Miles Day
and Wilson Eyre
. From 1885 to 1888 he was in the office of Cope & Stewardson
, took the year of 1889 to travel to England and Europe to sketch, then returned to Cope & Stewardson briefly in 1890 before switching to the Wilson Bros.
In his application for membership in the Philadelphia Chapter of the AIA, Baily noted that although all of the positions held in senior firms were primarily architectural in nature, he had also done some engineering work for both Cope & Stewardson and the Wilson Bros.
1890 was an eventful year for Baily. In that year he established an independent firm, working on his own for the first half of the year and, in July, joining Arthur Truscott, also late of the Wilson Bros., to form the partnership Baily & Truscott. This firm survived until 1904, when Truscott resigned to be replaced by George Grier Bassett, who had entered the firm in 1893 and risen to the status of silent partner in 1902. Baily & Bassett continued in operation until 1930, when Baily retired to devote himself to his ornithological pursuits.
While the work of both Baily & Truscott and Baily & Bassett relied chiefly on residential commissions, a healthy measure of churches, as well as work at Haverford College produced an output which was well-rounded. In style the work was primarily Colonial Revival, with a strong reliance on the Pennsylvania farmhouse type. Many of the buildings firmly associated with William L. Baily, however, indicate the influence of T. P. Chandler and Baily's European travel, with primarily French-influenced detailing and massing.
Baily had joined the T-Square Club in 1886 and the AIA in 1901. He was also a member of the Pennsylvania State Association of Architects and a stockholder in the Pennsylvania Academy of the Fine Arts. In addition, he served the University of Pennsylvania as instructor in its Department of Architecture, appearing on the Jury of Award during the 1895/96 term. In 1890 Baily founded the Delaware Valley Ornithological Club, which he helped to disband in 1936. An early photographer of birds and at one time an avid collector of bird skins, a practice which he later condemned, he donated his collections to the Academy of Natural Sciences in Philadelphia. During his retirement Baily cataloged and published a list of all of the bird species appearing on the Haverford College campus, at once combining his loyalty to Haverford with his love of ornithology.