The 2022 monkeypox outbreak in the United States is part of the larger outbreak of human monkeypox caused by the West African clade of the monkeypox virus. The United States was the fourth country, outside of the African countries with endemic monkeypox, to experience an outbreak in 2022. The first case was documented in Boston, Massachusetts, on May 19, 2022. As of August 22, monkeypox has spread to all 50 states in the United States, as well as Washington, D.C., and Puerto Rico. The United States has the highest number of monkeypox cases in the world. California has the highest number of monkeypox cases in the United States.