Settlers of present-day Allegheny County received land grants from the Commonwealth after William Penn and his descendants vested the land to the legislature. 

Maps show the individual who received the grant, the date the land was warranted and surveyed, dimensions and name the property was given by the title owner.

Information from the Warrantee Atlas of Allegheny County PA.

Resources:
www.Phmc.state.pa.us
www.historicpittsburgh.org