PHILADELPHIA — Union members planned to turn out by the thousands Saturday to support a second bill of rights for the American worker and express their disappointment in the Democratic Party for holding its national convention in North Carolina, a state they claim is decidedly unfriendly to unions and their goals.

Organizers of “Workers Stand for America” said they expect up to 20,000 people to attend the all-day event in Philadelphia that will bring in working families from Pennsylvania and neighboring states for speeches by Democratic lawmakers, a concert by Lucinda Williams and rallies with AFL-CIO President Richard Trumka and other unions.

Scores of workers dressed in green, orange and yellow T-shirts, some of them holding American flags, began arriving early Saturday next to the Philadelphia Art Museum steps made famous in the movie “Rocky.” The event begins next to the museum at Eakins Oval and will feature the introduction of what organizers call “America’s Workers Second Bill of Rights.”

Prominent labor leaders created the rally after what they said was their lack of input into planning for the 2012 Democratic Convention in Charlotte, N.C., which begins Sept. 4.