Large, gray colored rectangular box shaped craft floating in front of cloud bank in mid Missouri.I was returning from a camping trip Monday, July 3, 2017, pulling our camper. I was alone in my vehicle, my wife and daughter were following me in another vehicle. We were traveling eastbound on US Highway 54, approximately 5 miles south of Camdenton, Missouri. The highway runs fairly north at that point.The skies were clear with a white fluffy cloud bank several miles ahead of me. I saw what was clearly a large gray colored rectangular box shaped craft floating from my right to my left just this side of the cloud bank, moving in a southwesterly direction, And what I would guess to be several miles in front of me. This thing was immense but just how large was hard to tell because of the distance.I glanced at my watch, it was 12:25 PM.There are a lot of trees alongside the highway and this is a hilly area, so I lost sight of the craft a couple of times by going up and down the hills, but I saw it for approximately a total of 30 to 45 seconds, before I lost sight of it for good because of the lay of the land.I was looking for a place on the shoulder to pull over and stop and jump out and run back to tell my wife and daughter what I had just seen and when I did it was just before a T intersection with a road to the left, so I told my wife about what I had seen and told her to drive down that road and see if she could see the object which she did and she never saw it.I'll be 67 years old next month August, and I've been waiting all my life, knowing there are UFOs and extraterrestrials out there.Now I have finally seen a UFO, the real deal.((NUFORC Note: We spoke at length via telephone with the witness, and he seemed to us to be an exceptionally serious-minded person. Based on his command of the English language, we suspect that his is a very capable, and reliable, witness. PD))