Modern societal functions for meeting basic needs contribute to the lack of understanding many Americans have about agriculture's connection to human health and environmental quality. Consequently, this limited understanding has produced a need to measure agricultural literacy to develop programming or enhance existing agricultural educational efforts. Research literature has identified the need for agricultural literacy instruments to be developed that measure current understandings. The National Agricultural Literacy Outcomes (NALOs) served as the conceptual framework for the development of an agricultural literacy criterion referenced progressive measurement tool for grades 3-5. A theoretical framework using assessment models was used to develop items to measure agricultural literacy in three proficiency stages: exposure, factual literacy, and applicable proficiency. A modified Delphi method was used to create the Longhurst Murray Agricultural Literacy Instrument (LMALI) with the intent of assessing elementary student understanding of the NALOs. Items were tested with students from regional representative states using exploratory factor analysis, confirmatory factor analysis, and discriminant analysis in the investigation. The development process resulted in a validated 15-item instrument for grades 3-5. Overall, the instrument provides a way for educators and stakeholders to measure agricultural literacy based on proficiency stages within the five NALO themes.