This old mill town is best known for what it used to be, when textile factories on the Merrimack River provided employment for thousands of immigrants from Ireland, Russia and Greece.

That town is long gone, and a new one is fighting to emerge. Despite being home to a University of Massachusetts campus, only about 1 in 5 residents has a bachelor’s degree. The median household income is about $49,500, lagging national and state medians. Nineteen percent of the city’s 110,000 residents live in poverty.

“The strength of this community is the strength of our people,” said the city’s just-departed mayor, Rodney M. Elliott, a Democrat. “We’re not wealthy in terms of economic income, but we find strength in our people.”

This is the kind of city where billionaire Donald Trump likes to hold his presidential campaign rallies, and where his message seems to resonate most.