That 75-mile-per-hour sign seen below, and never seen in Ohio, is on I-25 south of Denver. It reminded me that the rules of the road can be very different depending on where and when you are. American Samoa has a maximum speed limit of 30 mph, parts of Texas State Highway 130 are posted at 85 miles per hour, during World War II, a national 35 mph "Victory Speed Limit" was enacted (ouch!), and between 1974 to 1987 we were limited nationally to 55 mph. The link below contains more info on SH-130 between Austin and San Antonio.