By 1878, with The Mulligan Guard Picnic, Harrigan & Hart settled down on Broadway and played in seventeen of their shows over the next seven years (until Harrigan and Hart split up). Though still broad and farcical, these shows featured music that was integrated with a more literary story line, together with the dialogue and dance, and the shows began to resemble modern musical comedy. Harrigan wrote the stories and lyrics, and Braham wrote the music. These shows were very popular especially with New York's immigrant-based lower and middle classes, who were delighted to see themselves comically (but sympathetically) depicted on stage. The action of the plays took place in downtown Manhattan and concerned real-life problems, such as interracial tensions, political corruption, and gang violence, all mixed together with broad, street-smart comedy, puns and ethnic dialects. Harrigan played the politically ambitious Irish saloon owner "Dan Mulligan", and Hart played the African American washerwoman "Rebecca Allup."
Harrigan married Annie Braham, David's daughter, on November 18, 1876. Their family continued in his footsteps, as son William Harrigan, daughter Nedda Harrigan, and granddaughter Ann Connolly all became Broadway performers. However, Harrigan's habit of hiring relatives soured his partnership with Hart, and they split up in 1885. Hart died at age 36 from complications caused by syphilis. Harrigan ultimately wrote the book and lyrics for more than twenty five Broadway musicals and continued writing and performing until 1893.
Harrigan 'n Hart, a Broadway show featuring songs written by Harrigan and Braham, played at the Longacre Theatre in 1985. It featured Tony award-winning Harry Groener as Harrigan and Mark Hamill (of Star Wars fame) as Tony Hart. It was nominated for 1985 Tony Award, Best Book of a Musical, Michael Stewart.