Weir was well known in the 1930s for opposing President Franklin D. Roosevelt's New Deal program, for resisting union organizing drives by the Amalgamated Association of Iron and Steel Workers and its successor, the United Steelworkers, and for challenging the legal authority of the National Labor Relations Board.

In 1941, accompanied by her sons and a daughter in law, she moved to Okeechobee County, Florida, and obtained a divorce on November 14, 1941 from Weir on the basis of mental cruelty and desertion.

[7] Weir suffered a severe heart attack at his vacation home on Jupiter Island, Florida in mid-January 1957.

[7][15] His health, vigorous up to that time, quickly declined and he retired as chairman of National Steel on April 24, 1957.

[2] They purchased the failing Jackson Sheet and Tin Plate Company in Clarksburg, West Virginia, for $190,000.

[3][18] Phillips died in a train crash a few months after the company was formed, and Weir took as a new partner John C. Williams, a Welsh immigrant who was in charge of all tin plate operations at the plant.

[2] That same year, Weir began building a company town next to Holliday's Cove, naming it Weirton.

[19] On September 27, 1929, Weir, Humphrey, and Fink agreed to form a new holding company, National Steel, through a stock swap.

[24] Section 7(a) of the National Industrial Recovery Act guaranteed workers in the United States the right to form a union.

The case was awaiting resolution when the Supreme Court declared the National Industrial Recovery Act unconstitutional on other grounds.

[26] When Congress passed the National Labor Relations Act (NLRA) in 1935, Weir said he would refuse to obey the law.

Weir did so, but then supported the formation of the new Weirton Independent Union (WIU) and quickly signed a contract with it.

In 1946, the United States Court of Appeals for the Fourth Circuit appointed a special master to collect evidence in the case.

On February 1, 1950, the special master reported that while Weirton Steel did not create the WIU, it did dominate it illegally.

Additionally, the special master found that Weirton Steel had blatantly interfered with workers' organizing rights at its plants.

[35] In November 1952, the Great Lakes Engineering Works launched the SS Ernest T. Weir, a straightdeck bulk carrier.

[36] Commissioned by National Steel,[36] at 690 feet (210 m) in length she was the longest ship of her class at the time of her construction.