There was an idea, held in many quarters, that Abraham Lincoln sent the troops into Baltimore as a deliberate provocation...

Thanks, Stim - but not quite. The troops from the North were sent THOrUGH Baltimore en route to Washington DC because that's the way the railroads ran, and rail was the fastest way to get troops to defend the capital with the transportation system of the time.

There was also an idea, held in many quarters (and may still be!) that the Moon Landing was faked in a movie studio.