how do i go about getting into my deceased fathers safety deposit box

The bank is correct, you will need a court order.  Procedures differ in each state (your local clerk of the appropriate court can help you with those), but basically I believe that you will have to start a court proceeding to administer your father's estate, and seek to be named administratrix.  Assuming that you are named administratrix by the Court (theoretically, other close relatives, such as the widow, can oppose the appointment), you will be able to get the box opened.  You should be aware that this doesn't mean that you will be entitled to keep what is in the box; you will be allowed to open the box as a representative of the estate, and will have to distribute its contents according to the laws of intestacy (how an estate is distributed if there is no will).  Although I don't know the Mo laws of intestacy, I would be shocked if they did not entitle the widow to a share of your father's assets.  Also, you will have an obligation to use any assets found in the box to first pay off any estate creditors, such as the IRS.  Indeed, it is possible that the Court may order that an IRS representative be present when the box is opened.