1820 January 0
Population: 7248; Allegheny County, 34,927.

1820 January 0
The city's Alms House was built.

1821 January 0
Turnpike was completed from Pittsburgh to Erie, via Butler, Mercer, and Meadville.

1821 January 0
The Pittsburgh Recorder, a Presbyterian journal, was first issued.

1821 June 0
Pittsburgh Medical Society was organized.

1822 January 0
N. Holmes and Sons, the city's first family-owned bank, was established.

1823 April 28
Henry Clay was a visitor. The Apprentice Library was established as Pittsburgh's first free public library.

1824 January 0
Western University of Pennsylvania conferred bachelor's degrees for the first time. There were six in the graduating class.

1824 January 0
The Councils passed an ordinance providing for a central city water system.

1825 January 0
Allegheny Theological Seminary was established in Allegheny by the Associate Reformed Presbyterian Church.

1825 April 7
Western Theological Seminary was founded in Allegheny City by Presbyterian Church.

1825 May 30
The Marquis de Lafayette arrived at the Mansion House for a two-week visit. One of the most spectacular social events was a ball held at Colonel Ramsay's Hotel on Wood Street at Third Avenue in honor of the French statesman.

1826 July 4
Composer Stephen Collins Foster was born at 3600 Penn Avenue.

1826 September 0
The city's first water reservoir was completed on Grant's Hill.

1826 December 0
Work was started on the Pennsylvania Canal.