El Capitan re-install, where did this data come from?

I restarted my iMac in OS X Recovery.

In Disk Utility, I erased my Macintosh HD.

I selected Reinstall OS X; it took several hours to download from the Internet.

I set up my iMac without iCloud with one user - me; All My Files: empty.

I ran Safari. My previous Favorites and Reading list showed up. In Contacts, one showed up. How can this be?