Without taking a ramp: That's an interesting challenge. Even Interstate 5, you have to take a ramp to continue on it, as the majority of lanes north of L.A. point towards 99 and Bakersfield.
If we're being a strict as that, it looks like 80 is out, though it looks like 101-80-76 will get you to from L.A. to Philadelphia. 10 runs from Santa Monica to San Antonio before getting lost in a freeway maze. And 40 is only Barstow, Calif to Memphis. So the answer would be "no".
If you had a looser definition of "without taking a ramp" to mean "not leaving a freeway", then any of 80, 10, or 40 will get you from coast to coast. There are several more useful routes depending on which corners you're trying to connect, as all of the Interstate Highways have no cross-traffic.
See also https://en.wikipedia.org/wiki/Lincoln_Highway which is an old, mostly forgotten road that was an early transcontinental car route.
If we're being a strict as that, it looks like 80 is out, though it looks like 101-80-76 will get you to from L.A. to Philadelphia. 10 runs from Santa Monica to San Antonio before getting lost in a freeway maze. And 40 is only Barstow, Calif to Memphis. So the answer would be "no".
If you had a looser definition of "without taking a ramp" to mean "not leaving a freeway", then any of 80, 10, or 40 will get you from coast to coast. There are several more useful routes depending on which corners you're trying to connect, as all of the Interstate Highways have no cross-traffic.
See also https://en.wikipedia.org/wiki/Lincoln_Highway which is an old, mostly forgotten road that was an early transcontinental car route.
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