This township was originally (1788) included in St. Clair and Mifiiin. June 20, 1843, Stephen Woods, James Scott and William Kerr were appointed by the court of quarter sessions to inquire into the advisability of forming a new township from portions of Jefferson, Mifflin, Upper and Lower St. Clair. The proposed territory (10,446 acres) was accordingly surveyed. It became a separate subdivision of the county by decree of court, February 24, 1844. Henry Baldwin, from whom the name is derived, was one of the most prominent of the early members of the Pittsburgh bar.

There was a strong German element among the early population, and this nationality predominates to the present. John Varner, Jacob Crady, John Stewart and William Wightman were among the earliest settlers.

Of other early families in the township the following are remembered:
Joseph Wilson and sons James, John and another;
Harvey McDonough and sons James, Hiram H. and William;
John Carr and son Samuel;
David Kennedy and sons Isaac and David;
Henry Beltzhoover and sons Melchor, John, William, Henry, Samuel and Daniel;
William Kennedy and sons David and Samuel;
John Martin and sons Samuel, James and John;
Brawdy and sons John, Aaron and George;
Alexander McCleary and son Alexander;
James McCleary and son James;
William Moore and sons James, William and Samuel;
George Cunningham and sons David, Jesse and others;
Francis Cooley and sons Robert, John, William, Francis and Samuel;
Horning and sons John and Jacob;
Henderson Whiteman and son Baldwin;
Thomas Verner and son Melchor;
Peter Catt;
Joshua Long and sons William and Alexander;
Robert Long, a brother of Joshua and son John;
Jacob Mait;
John Kincaid.
The following were residents prior to 1820, and some of them quite early:
Matthew West, James H. Hays, Johnson Glass, Thomas Lewis, John Redman, Daniel Risher.

Early in this century there were two gristmills in this township, both on Saw-Mill run, one at Castle Shannon and the other at Fairhaven. Both have gone to decay, and a steam mill has taken the place of the one at Fairhaven. A sawmill was located near each of these primitive gristmills. A fulling-mill stood a few hundred yards above the mill at Castle Shannon, and at an early day it was conducted by Thomas Roland, a son of John Roland, the owner of the gristmill.

Beck’s run, Street’s run and Saw-Mill run are the most important streams. While the land is valuable for farming and gardening, the underlying strata of coal constitute the great source of wealth. The mines contiguous to the Monongahela river are operated by J. D. Risher and the estate of James H. Hays, and in the valley of Saw-Mill run by the Pittsburgh & Castle Shannon Railroad company, John W. Ortman, president; E. J. Reamer, secretary and treasurer; S. Kaufman, vice-president, and Alexander Patterson, superintendent. The company was incorporated September 18, 1871, and the road, extending from Pittsburgh to Castle Shannon, a distance of six miles, was opened November 1, 1871. Of the other railroads in the township tbe Pittsburgh, Virginia & Charleston was opened in 1872, the Pittsburgh, McKeesport & Youghiogheny November 19, 1883, and the Baltimore & Ohio short line in 1883. The latter was originally chartered July 3, 1876, as the Pittsburgh Southern railroad, and was opened to Washington as a continuation of the Castle Shannon road. The branch from Glenwood to Einleyville, sixteen miles long, was built in 1883. The road was sold under foreclosure November 20, 1884, and purchased by the Baltimore & Ohio for fifty thousand dollars. It was subsequently reorganized under the present name. The portion of the old line between Castle Shannon and Finleyville, twelve miles long, has since been abandoned.

The village of Castle Shannon is pleasantly situated in the extreme southwestern part of the township. It comprises several hundred inhabitants, local stores and village industries, a recently completed Odd-Fellows’ hall, and a Methodist church. Carrick postoffice has existed since December 23, 1853; Engleart glassworks are in the vicinity, and the hamlet at this place is sometimes referred to as Engleartville. There are postoffices at Fairhaven and Redman Mills. Pine Grove is a rural hamlet on the Brownsville road, about the center of the township. There is a Methodist church at this place.

North Zion German Lutheran Church was originally built in 1812. Concord Presbyterian Church was organized in 1832. Spencer Methodist Church is also an old organization, while the Roman Catholic church is of recent origin.

There are several cemeteries, of which the latest, Zimmerman cemetery, comprises twelve acres. The population in 1860 was 2,746; in 1870, 3,104; in 1880, 4,373.