Every US state which does not recognise same-sex marriage is now facing legal challenges, following plans for filing in North Dakota.

Same-sex marriage is currently recognised in 19 states and the District of Columbia, and following the announcement of filings in North Dakota, all of the remaining 31 are facing legal challenges.

Five gay and lesbian couples in the US state of Alaska filed a lawsuit last Monday challenging the state’s ban on same-sex marriage, leaving only three states with unchallenged bans.

Then on Wednesday, four couples in the state of Montana filed a lawsuit challenging the state’s ban on same-sex marriage.

Following a filing by a lesbian couple in South Dakota the number dropped to just one.

Today, civil rights lawyer Joshua Newville announced he had been approached to file on behalf of couples in North Dakota, the last remaining state.

He told the Washington Post: “There will be a case filed challenging North Dakota’s same-sex marriage ban.”

Once the lawsuit in North Dakota is filed, there will be no states left with marriage bans, which are not subject to a legal challenge calling on them to repeal them.

Proponents of same-sex marriage have had an extensive winning streak in courts across the US, following the Supreme Court’s decision to strike down the Defence of Marriage Act (DOMA) last year.

Since that case, not a single ruling has found against the right of same-sex couples to marry, urging litigation in more and more states.

This week, judges in Oregon and Pennsylvania found in favour of same-sex couples, allowing them to marry.

US District Judge John Jones wrote in the Pennsylvania ruling: “We are a better people than what these laws represent, and it is time to discard them into the ash heap of history.”