Dengue viruses are mosquito-borne flaviviruses that circulate in nature as four related serotypes (DENV1-4). These emerging pathogens are responsible for an estimated 390 million human infections each year. The outcome of human DENV infection ranges from clinically inapparent disease (~75% of infections), to a self-limiting febrile illness, to severe disease characterized by hemorrhage and shock. Severe clinical manifestations of disease are predominantly associated with secondary infections by a heterotypic DENV serotype. The increased risk of severe disease in DENV-sensitized populations significantly complicates vaccine development, as a vaccine should confer protection against all four DENV serotypes. As the development of a neutralizing antibody response is a correlate of protection for successful vaccines for several other flaviviruses, eliciting a protective tetravalent neutralizing antibody response is a major goal of ongoing DENV vaccine development efforts. Understanding the neutralizing antibody response to infection and vaccination is an important step toward the development and evaluation of safe DENV vaccines. While considerable insights have been gained from studies of monoclonal antibodies, the individual contributions and dynamics of the repertoire of circulating antibody specificities elicited by infection and vaccination are poorly understood on a functional and molecular level. We studied polyclonal antibody responses elicited by monovalent DENV1 vaccination and sought to identify epitopes recognized by serotype-specific neutralizing antibodies. DENV1 structural gene variants were produced and screened for reduced sensitivity to neutralization by DENV1 sera but unaltered sensitivity to control antibodies. We identified amino acid residues that contribute significantly to type-specific recognition by polyclonal DENV1 immune sera. These findings provide an important step towards deconvoluting the functional complexity of DENV serology following vaccination.