What was westward expansion like in the north during the antebellum era?

i really do want to but i just don't know it i'm so sorry : (

accomplishment : zachary taylor’s was a national war hero in his battle in an mexican war

explanation:

he was known as a national war hero for his battles in the mexican war, taylor was elected as the 12th president of the united states in 1849. he led the nation during its debates on slavery and southern secession. after serving only 16 months in office, taylor died from cholera morbus on july 9,