What were america's early experiences with imperialism before 1899?

Texas--Japan--Alaska--Midway--China--Samoa--Hawaii--Spanish-American War: These areas were all targeted or obtained prior to 1899.

Technically, this could start with the first land purchase in 1803 with the Louisiana Purchase, if you want to go back that far. Texas was the first US annexation of a sovereign country in 1845. The Mexican-American War will follow where the US will gain the current Southwest. In 1858, Matthew Perry visited Japan which helped to create an economic relationship with Japan. Alaska was purchased from Russia in 1867 and Midway was annexed in the same year. In 1868, the US creates a trade agreement with China now referred to as the "Open Door Policy". In 1878, the US creates a treaty with the Samoan leaders to built a naval base in exchange for US protection of the islands. Hawaii was annexed in 1898 and also in the same year, the US will fight for Cuban independence in the Spanish-American War. After winning, the US received Puerto Rico, Guam, and the Philippines.