Born in Denver, Colorado, Pinkney graduated from Colorado A&M in 1927, majoring in horticulture and entomology. He then pursued graduate work in landscape architecture at Harvard, where he served as a field assistant to Morley Jeffers Williams, supervising excavations at Stratford Hall in summer 1932, and again from August to October 1934. Pinkney’s discoveries were essential to the reconstruction of the east garden, as well as the stable, springhouse, and entrance west of the house. In 1934 Pinkney received his master’s in landscape architecture and married Evelyn Robinson. The Charles Eliot Traveling Fellowship sent him for a year’s study in Europe (1934-1935), and he apprenticed with Olmsted Brothers and worked for a time with Arthur Shurcliff.
Pinkney arrived with his family in Austin, Texas, in 1939. One of his earliest commissions was the landscape for the second phase of construction (1940-1941) at the Rosewood Courts housing project. He designed the gardens of several local estates and residences, including the Joseph Renfro, Jr., House, the Leach House, and the Stanley and Emily Finch House, all in the 1940s. He planned much of Austin’s Allandale neighborhood between 45th street and Northland Drive, as well as bicycle trails running along Shoal Creek. He also designed the landscapes of several local schools, including Summit Elementary School, Perry Park Elementary, Murchison Junior High School, McCallum High School, Reagan High School, and Rosedale School. In his design of the grounds of the French Legation Museum in 1953, Pinkney showed sensitivity to the history of the site, leaving the gently rolling grounds largely open and unobstructed. His career in Austin spanned five decades.