A Detroit newspaper account states that the 1st Michigan Three Month volunteer Infantry Regiment made the deepest penetration of the Confederate lines at the 1st Battle of Bull Run. Is this a true fact?
Depending how you define "deepest penetration" an argument can be made that Orlando Willcox's brigade (which included the 1st Michigan) got closer to the Confederate line on Henry House Hill than other units did. The 1st Minnesota (Franklin's brigade) was also in the mix here. But I'm not sure anyone can say definitively which of those units got closest to the Confederates, and I don't think any of them actually penetrated the main Confederate position.