He was a young architect on the staff of architect George W. Springsteen, of Springsteen & Goldhammer, when that firm engineered the first limited-equity cooperative in New York City, the Amalgamated Housing Cooperative in The Bronx, in 1927. Jessor subsequently worked with Springsteen on the design on the Hillman Housing Corporation and was the architect for phase two of the United Workers Cooperative Colony; East River Housing Corporation with Springsteen again, depending on the source, Seward Park Housing Corporation; Rochdale Village in Queens and the Penn South complex in Chelsea, Manhattan. In one of his largest undertakings, Jessor was the major designer of Co-op City, the 15,500-unit cooperative development in The Bronx.