FACTBOX-Key facts about U.S. auto labor talks

(Reuters) - The United Auto Workers union has been negotiating a new labor contract with the troubled U.S. auto industry for the past several weeks and selected General Motors Corp GM.N as its target in the talks last week.

On Tuesday, negotiators for the union and GM opened a fourth day of marathon talks since the old contract expired on Friday.

Representatives of the Detroit-based automakers say they need sweeping concessions to keep production in the United States and head off even more wrenching restructuring.

The UAW, on the other hand, has said it will fight to protect the wages and benefits of an industrial middle class that it helped create in the United States.

Following are five key facts about the union and the automakers as talks continue:

* Founded in 1935, the UAW won recognition after a series of sit-down strikes in 1937 at GM's then-massive Flint, Michigan, plant. Both GM and Chrysler negotiated their first contracts with the union that year.

Ford Motor Co., which was fiercely anti-union under founder Henry Ford, was the last of the three U.S. automakers to recognize the UAW in 1941.

The turning point for UAW in its efforts to organize Ford was a widely publicized, violent skirmish outside Ford's Dearborn, Michigan, factory complex in what became known as the "Battle of the Overpass."

Security guards from Ford attacked UAW organizers, including Walter Reuther, when they attempted to pass out leaflets. The incident turned public opinion against Ford.

* Total UAW membership, which also includes workers outside the auto industry, has dropped to about 640,000 from a peak of nearly 1.5 million in 1979 as Detroit automakers and major manufacturers cut blue-collar jobs.

The union will be negotiating contracts for more than 180,000 workers remaining on the line at the three Detroit automakers after a wave of recent buyouts.

By contrast, the three big Japanese automakers employ some 59,000 mostly nonunion U.S. factory workers. Despite repeated attempts, the UAW has not succeeded in organizing the U.S. factories of Toyota (7203.T), Honda (7267.T) or Nissan

(7201.T).

* UAW head Ron Gettelfinger, a onetime Ford assembly line worker with an accounting degree, is leading the national contract talks with the automakers for the second time. He is regarded as a pragmatist who has shown willingness to offer targeted concessions to automakers.

Gettelfinger agreed to a UAW-controlled trust fund for retiree health care at supplier Dana Corp., a first of its kind for the auto industry, which has long sought to unload costly retiree health-care obligations.

Gettelfinger also endorsed Chrysler's sale to Cerberus Capital Management and agreed to work with the investor group even though he has often expressed a dislike for private equity funds, calling them "strip and flip" operations.