What you are seeing is the Williamsport Boom completed in 1851. It was about 7 miles long and could hold over a million logs! As can be seen above it divided the Susquehanna into a river navigation area on the right and a log run on the left. Log jams appeared along waterways of log navigation anytime there was a disruption in the navigation of the water or a heavy run of logs.This was a seasonal problem also during winter with the waterways freezing or during spring floods. Some were hugh and reached back on the waterways for miles. Because of the large amount of logs entangled it took weeks to free them using many long man hours of dangerous work with dynamite or whatever means at hand. Did you find the two men sitting in the jam? I suppose they were scratching their heads wondering what would be the best approach in getting this mess cleaned up.