May 20, 1993 - On this day, a 30-foot wide meteor came within 93,000 miles of hitting Earth. On the cosmic scale, that's a pretty close call. It's less than half the distance to the moon.
Even so, an object 30-feet in diameter probably wouldn't pose much of a threat to us, as it would most likely burn up in the atmosphere.
There are thousands of near Earth objects (NEOs) that NASA keeps an eye on. There's also a list for PHOs, or potentially hazardous objects.
Thankfully none of the above contains an item on a collision course with Earth anytime soon - but that doesn't mean we're out of the woods completely.