Population got larger, rapid development of rail roads and ports, and finally land seized from the Spanish land owners and the native tribes. :)
The Coining of 'Manifest Destiny' By the time Texas was admitted to the Union as a state in December 1845, the idea that the United States must inevitably expand westward all the way to the Pacific Ocean had taken firm hold among people from different regions, classes and political persuasions.
The answer is D - Thomas Paine
