The campaigns opposing and supporting gay marriage in California raised more than $82m (£56.3m) between them, making it the most costly social issue campaign in American history.
Proposition 8, which overturned a Supreme Court ruling allowing same-sex marriage, was approved by 52% of voters on election day, November 4th.
Hollywood stars such as Steven Spielberg and Brad Pitt donated large sums to the campaign opposing Prop 8 and the Screen Actors Guild voted to officially oppose the California ballot initiative.
The US Conference of Catholic Bishops donated $200,000 to ProtectMarriage.com, the coalition that gathered more than a million signatures to get Proposition 8 on the ballot.
While Mormons and evangelical Protestants also made sizable monetary contributions, the single largest religious donor was The Knights of Columbus, a Roman Catholic fraternal organisation, which gave $1.4m.
Legal challenges to Prop 8 will begin oral arguments on March 5th.
In May 2008, the California Supreme Court ruled against a previous Proposition approved in 2000 that defined marriage in the state as between a man and a woman.
The court ruled that laws that treat people differently based on their sexual orientation violate the equal protection clause of the California Constitution and that same-sex couples have the same fundamental right to marry as other Californians.
Proposition 8 challenged this ruling by explicitly denying gay people the right to marry.
18,000 same-sex couples got married before Prop 8 passed. Their marriages are still legal.