Gangs of New York (2003)
In terms of historical accuracy, the film is far from perfect, but the visuals are terrific. You will never forget Daniel Day-Lewis walking the Five Points in his Sunday best.
The Molly Maguires (2004)
As with most Hollywood films, this one is more interested in drama than historical accuracy. But the Molly Maguires were real, and the conditions they challenged were horrific. You may be inspired to hunt down the equally dramatic but less sensational real story.
Out of Ireland (1995)
This is a solid documentary that explores the before and after of Irish immigration: the conditions that prompted the exodus of more than a million people and the struggles and achievements that followed their arrival in America.