You know, I do not feel at all guilty about all that land that we evil Anglo-Americans stole from Mexico. Mexicans had had the land for some centuries and had not settled it enough to raise a good soccer team. When California was taken there were already more white men from the U.S. and Europe there than there had ever been Mexicans and such Mexicans as were there had little contact with or affection for Mexico City. And the Mexico that the U.S. went to war against in 1846 had a large and aggressive army led by a dictator who fancied himself a Napoleon and had made and in some cases carried out blood-curdling threats against the gringos. Indeed, then as now, Mexican national identity depended heavily on hatred of the people beyond the Rio del Norte Something many forget. It wasn't their land just because the Pope said so in 1495.
And for those in my family who left their parent's settlements on the Yadkin and went with Boone through the Gap, and those who descended from them or followed them, they always knew it was their land to settle and tame.
The trail doesn't end either.
Frontiers still exist, and the Americans are still pushing out into them.