The history of NACCHO dates back to the 1960s, with the formation of the National Association of County Health Officials (NACHO), an independent affiliate of the National Association of Counties. As the federal, state, and local public health systems continued to expand, NACHO combined with the U.S. Conference of Local Health Officers, an organization affiliated with the United States Conference of Mayors, to form NACCHO in 1994. This unified organization more closely represents all governmental local health departments, including counties, cities, city/counties, districts, tribes, and townships. In 2001, NACCHO expanded its scope to include tribal public health agencies serving tribal communities on reservation lands. Today, NACCHO represents 2,800 local health departments.