I like the US from about 1850 to 1940. There was just a huge sea change in the understanding of the Constitution, economic institutions, and development in the country. It's a fascinating period to learn about. A lot of the conflicts from that time are still driving politics to this day. Right now we're basically in a reversal of Constitutional understanding back to a Lochner era reading where civil rights aren't important but economic rights of the elites are paramount. This is basically con law from 1939 to 1870 in reverse.