1870 January 0
The 642-foot Monongahela Incline, first in the city, was completed to the top of "Coal Hill" (Mount Washington).

1870 January 0
Jacob, Henry, Morris, and Isaac Kaufmann, German immigrants with $1500 between them, opened a men's clothing business in an I 8-by-28 foot storeroom at 1918 Carson Street, primarily to serve puddlers of the nearby Jones and Laughlin steel mill (Kaufmann's Store, incorporated in 1871).

1870 January 0
The Pittsburgh Coal Exchange was chartered for coal companies engaged in river transportation.

1870 January 0
Allegheny Bar Association was incorporated.

1870 January 0
The establishment of Pittsburgh titles for land belonging to the Penns was completed.

1870 January 0
Population: 86,076; Allegheny City, 51,180; Allegheny County, 262204.

1870 January 1
The Old Drury Theater closed its doors after 37 years of service.

1870 January 2
Judge Thomas Mellon, the father of Andrew W. and Richard B. Mellon, retired from the bench to open a private banking establishment under the name of T. Mellon and Sons on Smithfield Street near Sixth Avenue.

1870 January 17
The first professional teachers organization was established in the city.

1870 April 6
The Pittsburgh and Ormsby Passenger Railroad Company was incorporated to construct a railway from the borough of Ormsby to a Market Street terminal.

1870 June 13
Pittsburgh's first paid fire department was organized.

1870 September 28
Pennsylvania College for Women opened under the auspices of the Presbyterian Church.

1870 October 13
The first Pittsburgh Weather Bureau was established by the War Department and Signal Corps at 25 Fifth Avenue.

1871 January 0
The Pittsburgh Grand Opera House, on Fifth Avenue, was completed.

1871 January 0
Making of steel castings from crucible steel was begun at the Pittsburgh Steel Casting Company.