There are several Federal and state laws that benefit married couples. Some examples include the right to:
File joint income tax returns with the IRS and state taxing authorities.
Create a "family partnership" under federal tax laws, which allows you to divide business income among family members (this will often lower the total tax on the income).
Create a marital life estate trust.
Receive spouse's and dependents' Social Security, disability, unemployment, veterans', pension, and public assistance benefits.
Receive a share of your deceased spouse's estate under intestate succession laws.
Claim an estate tax marital deduction.
Sue a third person for wrongful death of your spouse and loss of consortium.
Sue a third person for offenses that interfere with the success of your marriage, such as alienation of affection and criminal conversation (these lawsuits are available in only a few states).
Receive family rates for insurance.
Avoid the deportation of a non-citizen spouse.
Enter hospital intensive care units, jails, and other places where visitors are restricted to immediate family.