Ralph Spencer Twitchell (1890-1978) was one of the founding members of the Sarasota School of Architecture. He is considered the father of the group of modernist architecture practitioners, that includes Paul Rudolph and Jack West, and other modernist architects who were active in the Sarasota area in the 1950s and 1960s like Ralph and William Zimmerman, Gene Leedy, Mark Hampton, Edward "Tim" Seibert, Victor Lundy, William Rupp, Bert Brosmith, Frank Folsom Smith, James Holiday, Joseph Farrell and Carl Abbott. He bridged the more traditional architecture of his early work in Florida during the 1920s with his modernist designs that began in the 1940s.
Twitchell first came to Sarasota as the representative of New York architect Dwight James Baum to manage the final stages of the construction of John Ringling's Cà d'Zan, a marble and concrete palace on the Sarasota Bay. He also worked with Baum on the Sarasota County Courthouse. Following this, Twitchell purchased 13 lots in the Ravellan Gardens bayside neighborhood of Sarasota and designed Mediterranean architecture homes on these lots. Lauded in the press, the homes were financially problematic as the Florida real estate bubble of the 1920s had collapsed. Some of the homes survive and have been included on the National Register of Historic Places.
Twitchell moved permanently to Sarasota in 1936 and opened an architectural office there. In the summer of 1941, he hired Paul Rudolph, 28 years his younger, after Rudolph completed his studies at the Alabama Polytechnic Institute (today, Auburn University) and before he began attending Harvard University's Graduate School of Design. Rudolph returned to Twitchell in 1946 and partnered with him until 1951. During this time, Twitchell and Rudolph designed many ground-breaking private residences that are the foundation of the Sarasota School of Architecture, including the Miller House and Guest Cottage (1947), the Revere Quality House (1948), the Lamolithic Houses (1948), the Healy Guest House - nicknamed "The Cocoon House" - (1949), and the Leavengood Residence in St. Petersburg, Florida (1951). The Revere Quality House was the first poured concrete house on Siesta Key and had rooms that opened out onto terraces and landscaped areas. This open design and use of glass walls became characteristics of the Sarasota School of Architecture. 
Twitchell and Rudolph parted ways in 1951. Between 1953-1954, Twitchell partnered with another Sarasota School master, Jack West and between 1959-1965 with his son, Tollyn Jules Twitchell. Ralph Twitchell died in Sarasota, Florida, on January 30, 1978.
- MacKinlay Kantor Residence, Siesta Key, Sarasota, Florioda, 1936
- Showboat Hosue, Lake Louise, Florida, 1937
- Lido Beach Casino, Siesta Key, Sarasota, Florida, 1940 (with Arthur Saxe, demolished in 1969)
- Twitchell Residence at Big Pass, Siesta Key, Sarasota, Florida, 1941 (with Paul Rudolph) (destroyed)
- Miller Guest House, Casey Key, Sarasota, Florida, 1947 (with Paul Rudolph) (demolished)
- Revere Quality House, Sarasota, Florida, 1948 (with Paul Rudolph)
- Lamolithic Development, Siesta Key, Sarasota, Florida, 1948 (with Paul Rudolph)
- Deeds Residence, Siesta Key, Florida, 1949 (with Paul Rudolph)
- Burnette Residence, Sarasota, Florida, 1950 (with Paul Rudolph) (destroyed)
- Healy Guest House - “The Cocoon House” - Siesta Key, Sarasota, Florida, 1950 (with Paul Rudolph)
- Leavengood Residence, St. Petersburg, Florida, 1951 (with Paul Rudolph) (destroyed)
- Hudson Beach House, Venice, Florida, 1953
- Knott Residence, Yankeetown, Florida, 1953 (with Jack West)
- Andrews Residence, Sarasota, Florida, 1959
- Merton Wilcox Residence, 1965, Twitchell's last house designed on Siesta Key