Why won't my iCal calendars display in the same window?

Google calendars other than your default calendar are treated as delegated calendars by iCal. To get them to open in the main screen go to iCal > Preferences > Accounts, select your google account, click the tab for Delegation, then check the boxes next to the calendars you want to display in your main calendar window.

Now in the upper left hand corner of the iCal window, click the Calendars button which brings up the pop-up allowing you to select which calendars are visible. Check the box for the calendars you want to view. You can return to this pop up at any time to change the calendars you're seeing at any given time.

Having them show up as delegates is okay, but it's nicer if they show up with the other Google calendars, and that also makes for a better experience on an iOS device. To do that, go to https://calendar.google.com/calendar/syncselect (which isn't linked anywhere from the main Google Calendar settings page, even after many years), and check the boxes for all of the Other Calendars you want exported.

I feel like I rediscover this secret every few years.