Having been Spain's closest colony to the United States until 1898, in the first part of the 20th century Cuba continued to develop with the influence of big investments, the creation of various industries, and growing travel to support mostly US interests and corporations. Its proximity (roughly 90 miles (140 km) from the Florida Keys) and close relationship with the United States also helped Cuba's market economy prosper fairly quickly. As relations between Cuba and the United States deteriorated rapidly after the Cuban Revolution of 1959 and the resulting expropriation and nationalization of businesses, the island became cut off from its traditional market by an ongoing embargo and a travel ban was imposed on U.S. citizens visiting Cuba. The tourist industry declined to record low levels within two years of Castro's accession to power.