Topo maps are here:
http://historical.mytopo.com/
Also found Orange in the Sanborn maps here:
http://sanborn.umi.com/
Logon ID - Sanborn
Password - welcome
Why are you searching for the land fill? And what do you hope to find? People have been living in the Orange area since about 1700, but they probably didn't have a public/common trash dump until the city started offering public services (early to mid 20th C). If you're looking for really old bottles and stuff, people usually had their own trash dumps on some remote part of their property or sometimes dumped stuff down the privy hole.
DCMatt