Polk died, some say from overwork, though cholera was part of the problem, shortly after leaving the office of the presidency in 1849. This meant he did not have much time to see how his presidency impacted the future, nor did he have much time to assess his successes and...
Polk died, some say from overwork, though cholera was part of the problem, shortly after leaving the office of the presidency in 1849. This meant he did not have much time to see how his presidency impacted the future, nor did he have much time to assess his successes and failures after his presidency ended.
Additionally, Polk was not one to blame himself for problems. He worked very hard and tended not to be very reflective about what he had done wrong. He tended instead to view himself with satisfaction, probably an important trait in anyone hoping to succeed in the presidency.
If there was one area in which Polk did feel a sense of failure, it was in not succeeding at formally bringing the New Mexico and California territories into the United States to the extent he wished. Polk had a very strong conviction that to survive and thrive, the United States must incorporate as much of the North American land mass as possible into the United States. He pursued aggressive policies to that end, such as the controversial Mexican-American war that led to the annexation of Texas as a slave state. In fact, he was later criticized for being so bent on expansion that he let the slavery issue go out of control.
In his address to Congress on December 5, 1848, just a few months before he left office, he forcefully stated his regret at the failure to establish governments in new territories:
It is our solemn duty to provide with the least practicable delay for New Mexico and California regularly organized Territorial governments. The causes of the failure to do this at the last session of Congress are well known and deeply to be regretted. With the opening prospects of increased prosperity and national greatness which the acquisition of these rich and extensive territorial possessions affords, how irrational it would be to forego or to reject these advantages by the agitation of a domestic question which is coeval with the existence of our Government itself ....
While Polk tries to blame Congress, as president, this failure in one of his core policy objectives also lands squarely on his shoulders.
He also writes about this in his July 27, 1848, diary account, expressing regret that a territorial bill establishing governments in Oregon, California, and New Mexico is likely to be defeated in the House of Representatives.
Polk was aware that he failed to extend the United States as far as he wished; however, he was unaware of the extent to which he created problems by subordinating slavery issues to this goal. California did become a state in 1850, but Polk did not live to see this.
If you need more information, I suggest you go to Polk's diaries (linked below).