If my husband and I are separated, can he legally keep possession of the personal property that I left behind?

There is no mine or his when you acquired property together in a marriage and or converted items to marital use during a marriage. So if your dog was acquired during the marriage (the fact it is in your name is not the conclusive reason it should be given to you), you need to go through the court process to obtain a lot of your personal belongings back and have it set out in a divorce decree.  Separation is in most states considered the time when you can begin to change the characterization of income, debt and assets acquired from marital to separate. The reason is because separation is defined as the time period when you live separate and apart from each other with no possibility of reconciliation. If your spouse fights and wins for an earlier separation date, anything he earned after that date is his separate property, anything he acquired after that date is his separate property and so is the debt. If you purchased the computer during the marriage, it is considered a marital asset unless you can show for example you were the primary or sole user of that particular computer. Even items left in a personal storage facility can be considered marital assets, especially if the personal storage facility was obtained during marriage. Try talking to the storage facility to see if you can gain access to what may be rightfully yours. It is a longshot though so the only ways to try to get your items are to either ask him and put it in writing or go to court to obtain a divorce decree or separation order.