Back in the 70s when I lived in central Indiana, and when I was also in Boy Scouts and learning about maps and compasses and stuff, the zero declination line ra

Back in the 70s when I lived in central Indiana, and when I was also in Boy Scouts and learning about maps and compasses and stuff, the zero declination line ran right through Indiana such that magnetic north and true north were effectively the same. In fact, a historic declination viewer confirms that in 1976 the zero line ran within single-digit miles of my house. (It now looks to run through the middle of Missouri.) So I never used that little declination arrow on the paper maps. I knew how it worked in theory, but had no practical application. A move to North Carolina necessitated that I get handy with that. Then a move to Seattle made me realize how far off a magnetic compass can be. It doesn't look like I'll live long enough for the zero line to get to Seattle, though, so I better get used to it.