1920 January 0
"Population: 588,343; Allegheny County, 1,018,463.

1920 January 2
A total of 233 suspected leaders of the Communist movement in Pittsburgh were arrested by federal agents in two days as part of a nationwide roundup ordered by Attorney General A. Mitchell Palmer.

1920 January 11
Judges wore gowns in court for the first time in Allegheny County.

1920 January 13
The Pennsylvania Railroad announced a $100,000,000 improvement and expansion program for the Pittsburgh area.

1920 January 15
Henry Ford came to Pittsburgh to place in person $15,000,000 worth of steel contracts in the area.

1920 January 20
The national steel workers' organizing strike ended after the fourth month without achieving its objective.

1920 January 22
B. F. Jones, Jr., of Jones and Laughlin Steel, purchased the old Monongahela House for $750,000 with the intention of converting it into an office building.

Courtesy of the Historical Society of Western Pennsylvania

1920 February 28
The great Italian tenor, Enrico Caruso, sang at the Syria Mosque.

Courtesy of the Historical Society of Western Pennsylvania

1920 March 1
The United States Supreme Court declined to dissolve the United States Steel Corporation and its subsidiary companies as asked by the federal government in a suit alleging violation of antitrust laws.

1920 April 28
Dr. John Brashear, noted astronomer and maker of astronomical lenses and other scientific instruments, died at 80 at his South Side home.

1920 June 0
The Citizens Committee completed the first of a series of six major studies leading toward a comprehensive city plan, issued a report analyzing the city's recreational deficiencies, and recommended a system of playgrounds.

1920 November 2
Allegheny County women appeared at polling places to cast their first ballots.

1920 November 2
Station KDKA, first licensed radio broadcasting station, gave the Harding-Cox election returns as its first scheduled broadcast Allegheny County gave Harding a plurality of 105,000 over Governor Cox.

1920 November 6
Repeated landslides occurred below Bigelow Boulevard as rainfall continued; engineers waged a losing fight in their efforts to stop the slides and protect Pennsylvania Railroad tracks.

1920 November 20
General George W. Goethals, builder of the Panama Canal, on invitation of city officials, came to Pittsburgh and inspected the Bigelow Boulevard slide. He reported: "The situation will prevail until all has come down."