4th Regiment, Pennsylvania Infantry (3 months, 1861)
This regiment was organized at Harrisburg April 20, 1861. 
Companies in this Regiment with the Counties of Origin
Men often enlisted in a company recruited in the counties where they lived though not always. After many battles, companies might be combined because so many men were killed or wounded. However if you are unsure which company your ancestor was in, try the company recruited in his county first.
The Fourth Regiment was recruited in:
Company A - many men from Wilkes-Barr, Luzerne County
Company B - many men from Wyoming County
Company C - many men from Clinton County
Company D - many men from Union County
Company E - many men from Bradford County
Company F - many men from Luzerne and Bradford Counties
Company G - many men from Columbia County
Company H - many men from Luzerne County
Company I - many men from Luzerne County
Company K - many men from Luzerne and Schuylkill Counties
National Park Service, The Civil War Soldiers and Sailors System, is searchable by soldier's name and state. It contains basic facts about soldiers on both sides of the Civil War, a list of regiments, descriptions of significant battles, sources of the information, and suggestions for where to find additional information.