Labor Day was once the nation’s most blatantly political national holiday — created by the trade-union movement to celebrate the right of working people to bargain collectively and to stage strikes to press their demands. But no more, for good reason.

Even before Congress created the federal holiday in 1894, New York hosted the nation’s first Labor Day parade as 10,000 workers took off from their jobs to march from City Hall to Union Square. As the movement grew, so did the parades and celebrations.

How times have changed. Today, Labor Day is largely an occasion for sales, end-of-summer cookouts and back-to-school preparations. Why? Because the movement has become as irrelevant to most Americans as the medieval guilds that preceded it — and all too often a protector of privileges rather than a force for the oppressed.

In 1954, more than one in three American workers was a union member. Today, it’s barely over 6 percent of private-sector workers — but, in a huge shift, more than a third of public-sector workers (nearly 35 percent). Indeed, more than half of all union members today work for government: 7.2 million, vs. 7.1 million ........