If you click on the "Topeka" logo (or any special Google logo) it will give you the backstory on why they chose it.
Spoiler!
This one is because Google is offering to install gigabit speed fiber internet to one lucky city, and a whole bunch of municipalities are doing crazy stuff to get their attention. Topeka, Kansas officially changed their name to Google, Kansas for the duration of the search, so for April fools, Google returned the favor. Funny, but they could do better, lol.