The distance across the United States, from Florida to Washington, is 2,802 miles. This is the longest straight line distance across the United States.
The straight line begins in Jupiter, Florida, at the coordinates 80 degrees 4' 29" west and 26 degrees 57' 11" north. The straight line ends in Ocean Creek, Washington, at the coordinates 124 degrees 41' 38" west and 48 degrees 21' 44" north. Mark Nandor was the first person to find the longest straight line in the United States using a gnomonic projection.
If someone wanted to travel this straight line distance of 2,802 miles across the United States then he would actually have to travel 3,431 miles. This is because there would be a 200 to 600 foot hike at both ends of the United States to get from the ocean to the roads. This is also because although a straight line on a sphere can be mapped out online or on a map, there is not a straight line road that runs from Florida to Washington. The person driving, biking or walking would need to take roads that veered slightly off path from time to time. However, a person might be able to fly the distance in a straight line with the proper resources.