The state historic preservation office (SHPO) is a state governmental function created by the United States federal government in 1966 under Section 101 of the National Historic Preservation Act (NHPA). The purposes of a SHPO include surveying and recognizing historic properties, reviewing nominations for properties to be included in the National Register of Historic Places, reviewing undertakings for the impact on the properties as well as supporting federal organizations, state and local governments, and private sector. States are responsible for setting up their own SHPO; therefore, each SHPO varies slightly on rules and regulations. To link these differences with the SHPOs, the National Conference of State Historic Preservation Officers (NCSHPO) was created as a “point of contact” according to the National Historic Preservation Act.
More information on the Wikipedia page