Within a short time, she started a private co-educational school called the Sierra Seminary, which as the first legally chartered school in Nevada.
In 1875, Clapp was the successful bidder for the contract to erect an iron fence around the state capitol.
In 1877, Clapp and co-worker Eliza Babcock opened Nevada’s first kindergarten in Carson City. A decade later, Clapp was appointed professor of History and English at the new University of Nevada in Reno, becoming the first woman faculty member at the university.
In addition to teaching classes, Clapp also managed the women’s dormitories and the school library. Clapp was also a dedicated suffragist, working tirelessly for women’s voting rights for several decades. When she died in 1908, the Reno Evening Gazette wrote “it is doubtful if any single individual has had a wider influence in the forming days of Nevada than Miss Clapp.”