The United Provinces of Central America breaks up in 1839 into the five independent nations of Costa Rica, Nicaragua, Honduras, El Salvador and Guatemala. The region became economically dependent on the United States. American military forces, the marine corps, frequently intervened in the region.

Benito Juarez ruled Mexico between 1858 and 1872. He abolished the privileges of the church which resulted in a civil war between conservative supporters of the church and the liberals supporting Juarez. A coalition of European powers led by France intervened. In 1863, the Archduke Maximilian of Austria was made emperor of Mexico, backed up by the French army. American pressure forced France to withdraw its troops and by 1867, the forces loyal to the emperor were defeated, and Maximilian himself was executed by the order of Juarez. Porfirio Diaz ruled as president of Mexico from 1877- 80 and 1884-1911, after which there was renewed unrest and rebellion.

A canal, to be cut across the Panama isthmus, joining the Pacific and the Atlantic oceans, is first proposed by the French in the last third of the 19th century.

Construction is begun in 1881 by Ferdinand de Lesseps (builder of the Suez Canal), but disease and rugged terrain in the rain forest of Panama makes working conditions extremely difficult, resulting in a high death rate among the European workers. De Lesseps' company goes broke and work on the canal is abandoned in 1893.

Then in 1901, the United States agrees to take over the job. A revolution in Panama against Colombia is provoked by the Americans. Panama declares its independence, but is really controlled by the United States. Work on the Panama canal begins in 1904, and is completed after ten years in 1914, one of the chief engineering works of the 20th century.

In 1898, the Spanish-American War breaks out. The Americans invade Cuba in support of an anti-Spanish rebellion there (begun in 1895). In 1902, Spain admits defeat and Cuba is made an independent republic under American protection. The Americans also annex Puerto Rico from Spain.