State laws differ so it would depend upon your specific state's equipment laws and your situation.

For example as part of the inspection process in New York they check your mirrors. They check mirror locations for proper mounting, cracks, breaks, and/or discoloration. In NYS the following is true for mirrors:

• Model year 1970 and newer - must have a left outside mirror and an inside mirror, or both left and right outer mirrors
• Model year 1968 and newer - must have a left outside mirror
• 1967 and older - must have one mirror that is either an inside mirror or a left outside mirror

It is also noted that any vehicle that has a permanent obstruction of the view through the rear window (Example: a truck or van) must have both a left-side mirror and a right-side outside mirror in New York State.

Other states have similar restrictions and in some cases if you have a restriction on your driver's license you may be required to have side mirrors even if they are not normally required by state laws. For example I have a relative in Ohio that is hard of hearing and they have mentioned that due to this physical problem they are required to have side mirrors on their vehicles.

To find out what your state's requirements are regarding motor vehicle equipment, and in particular if a passenger side is absolutely required, contact your local Department of Motor Vehicles.