Answer:
Great Britain, France, Spain, and Mexico among others
In 1869, The Transcontinental Railroad was completed
Step-by-step explanation:
Shortly after gaining independence, Great Britain ceded land west of the Appalachian Mountains, South of the Great lakes and East of the Mississippi River to the United States
In 1803, the United States brought Louisiana from France (It is called the Louisiana Purchase)
On February 22, 1819, the Adams-Onis treaty was signed which led to the annexation of Spanish Florida to the United States
After a US victory the Mexican-American war (1846-48), Mexico ceded the land that makes up the current states of California, Arizona, New Mexico, Nevada, Colorado, Utah, and Wyoming
The Transcontinental Railroad was a series of Railroads from the east of the nation to the west