Under stoops or near out buildings are also good spots to check. Look up the histories on any old bandits that operated in your area. See if you can find any information on where they used to hang out. There are a lot more treasures out there than have ever been reported. All you have to do is spend some time on research.
Ghost Towns are another good source of coins and relics.
To work a Ghost Town you need a lot of patience because you will have to dig a lot of garbage. The chat area will be open every day all day. You can go here to find a schedule of chat events and join in. Also if you have a comment or question for others you can go to the Bulletin Board and post a message.