The vast majority of US states to do permit common law marriage. Many localities do support various types of domestic partnerships. In the West marriage has evolved from a life-time covenant that can only be broken by fault or death to a contract that be broken by either party at will. Other shifts in Western marriage since WWI include:

Property acquired since marriage is not owned by the Title-holder. This property is considered marital and to be divided amoung the spouses by community property law or equitable distribution via the courts. There is a growing debate about the form(s) that marriage should take. Two of the most hotly-debated variants are same-sex marriage and polygamy.

Husbands may no longer physically discipline/abuse their wife

Out-of-Wedlock children have the same rights of support as legitimate children

In most states rape can legally occur within marriage and be punished

Both spouses have a formal duty of spousal support (no longer just the husband)

Unlike the 1800s women not men get child custody over 80% of the time.

Marriage sometimes establishes the legal father of a woman's child; establishes the legal mother of a man's child; gives the husband or his family control over the wife's sexual services, labor, and/or property; gives the wife or her family control over the husband's sexual services, labor, and/or property; establishes a joint fund of property for the benefit of children; establishes a relationship between the families of the husband and wife. No society does all of these; no one of these is universal.