I also basically re-invent a tiny 50 line router for every web project. Hardly ever go beyond "Map URL -> Page" and "Map URL + Parameters -> Page with properties", and when you do, knowing 100% how it works helps a lot.

I also agree it isn't a hard problem, but personally I'd say you got the flow the wrong way around. You don't want to "synchronize state to the page URL" but rather treat the page URL as something you create state from, so it works both when you navigate there by pressing anchor tags, or the user manually enters the URL, and it gets a bit easier to manage.

Basically, URL is the top-level state, and from there you derive what page, then render that page, rather than the other way around.