@1oldman2, I have a question: do you wish for the answer in terms of
(a) roads, trains, ferries and boats;
(b) as the crow flies; or
(c) tunneling through the earth?
Each will give a somewhat different answer.
I'm guessing you don't want (a) because there are so many possible routes that it would be tough to meet the 200 mile margin of error.
"As the crow flies" seems more reasonable. The problem isn't really simple though since Mercator map projections will not give you accurate distances. In other words, if you are using a Mercator map, you can't rely on its "scale" for such large distances, since the scale will vary depending on which part of the map you are on. And, in Mercator maps, the shortest distance (on the surface) between two points does not follow a straight line -- it follows a great circle. One
could overcome this by breaking each great circle segment into many smaller segments, each with its own scale, and adding the results. Or one could use geometry, by first modeling the cities to coordinates on a sphere and then calculating arc lengths. Either way is doable, but not a no-brainer.
[Edit: One might be able to measure (b) somewhat easily if one has access to globe. One could use the globe together with a ribbon (or edge of a piece of paper) to take the measurements.]
Finally, one could interpret the distances as the true shortest path in three dimensions between the cities (c) -- not limited to the tangent space of a sphere. In other words, you can tunnel underground/underwater. I'm guessing you don't want this option.
(Options
b and
c could be even more accurate by using oblate spheroid geometry instead of spherical geometry. But that would be getting just crazy mathy.)