(Reuters) - Ballot initiatives allow voters to directly decide whether to change state laws or amend state constitutions.
The proposals are placed on the ballots in presidential or congressional election years. Following are results of some of the initiatives on Tuesday's ballot.
CALIFORNIA - Voters approved an amendment to the state constitution recognizing marriage as only between a man and a woman. Gay rights activists immediately filed legal challenges.
The amendment overrides a ruling by the California Supreme Court in May allowing gay marriages, and is viewed as a key battle in the nation's "culture war" because the state is seen as a trendsetter for the rest of the country.
Voters in Florida and Arizona also passed gay marriage bans.
ARKANSAS - Voters approved a ballot measure banning unmarried couples from adopting or serving as foster parents. The measure was seen as a salvo against same-sex marriage and gay couples.
NEBRASKA - Voters passed a constitutional amendment banning state and local governments from giving preferential treatment on the basis of race, sex, ethnicity or national origin.
A similar initiative in Colorado was still too close to call late on Wednesday.
SOUTH DAKOTA - Voters rejected a ban on abortion except in cases of rape, incest or if the pregnancy threatens the mother's health or life.
COLORADO - Voters rejected by about a three to one margin a measure that would have made abortion the legal equivalent of murder by defining human life as beginning at conception.
CALIFORNIA - A ballot initiative requiring more humane treatment of farm animals passed by a landslide.
Proposition 2 amends the state constitution to require more living space for some farm animals, including pregnant pigs and egg-laying hens. Opponents argued that the measure could cripple California's $300 million egg production industry.
CALIFORNIA - Voters refused to authorize up to $5 billion in incentives to buyers of high fuel-economy and alternative-fuel vehicles. Proposition 7, which would also have approved incentives for developing renewable energy technologies and fuels, lost by a huge margin.
(Sources: Reuters, California Secretary of State, Florida Department of State, South Dakota Secretary of State, Family Research Council, American Civil Rights Institute, Ballot Watch, National Conference of State Legislatures)
Compiled by Dan Whitcomb; Editing by Eric Beech