The First Railroad in the US, it was incorperated in 1828, to haul grain and coal to the port of Baltimore from the Ohio river, which was reached in the 1850's.
The first use of a steam locomotive happened on the stretch between Mt Clare and Ellicott City, in the form of a race between a horse drawn cart and the Tom Thumb.
The B&0 ceased to exist in 1989, when it was formally merged into CSX.