If I found a dollar bill, would it be illegal to keep it ?
No, it is not illegal to keep a dollar bill if you found it. However, if you found a large amount of money, such as a wallet with a significant sum of money, it is your legal obligation to try and locate the owner of the lost property and return it to them. Keeping lost property without making a reasonable effort to return it could potentially be considered theft or larceny, depending on the circumstances.

In general, it is always a good idea to try and return lost property to its rightful owner, as it is the honest and ethical thing to do.
What is the legal obligation of returning lost property? Can finding and keeping a small sum of money be considered theft?