Not sure about Allegheny Co, but if you are attempting to check PA records online, you won't find many. You may want to contact Marlene Bransam to see if she has found anything. She is on this forum. Also, Family Search has uploaded many records to their website, but the PA records are not very helpful. It may help if you are check surrrounding states like WV, KY and of course OH. Their records are numerous. I have been find lots of info there since the records were uploaded the end of April. You click on the Search tab and then the pilot search tab.

You mentioned river towns. Also remember that RT 40 which was the first national road went thru Fayette and Washington Counties, PA. There are were stops in these counties on the UGRR. These counties are south of Allegheny.

Linda