A random bit of trivia about Portland (and it probably explains a lot of the off-axis streets in other cities) is that there was a section laid out to align to

A random bit of trivia about Portland (and it probably explains a lot of the off-axis streets in other cities) is that there was a section laid out to align to true north, and another section of town that aligns with magnetic north. Eventually, those parts merged so now there's some weird pizza-slice shaped blocks (near Powell's, for instance). Magnetic north changes over time, so effectively our city streets become an effectively permanent record of the Earth's magnetic field at a specific moment in time, not all that unlike the rocks that store the magnetic alignment when lava cooled and we use to correlate seafloor spreading with magnetic field reversals.