1. Marriage has always been defined as the union of a man and a woman.
Up to this year (2012), same-sex marriage has never been legal in Maryland.
(That is, Maryland has never issued licenses for civil "marriages" between two persons of the same sex.)
In 1972, the Maryland Attorney General issued an opinion stating,
In 1973, the Maryland General Assembly made that definition of marriage explicit by adopting Senate Bill 122, which said,
2. There is no constitutional right to same-sex marriage.
In 2007, the Maryland Court of Appeals (the state's highest court) ruled that the Maryland Constitution does not require recognition of same-sex marriage, declaring:
"There is no fundamental right requiring the State to sanction same-sex marriage"
"[T]he State's legitimate interests in fostering procreation and encouraging the traditional family structure in which children are born are related reasonably to" defining marriage as being between a man and a woman. 
3. A bill to legalize same-sex marriage in 2013 has been signed into law.
In 2012, the General Assembly passed, and the Governor signed, House Bill 438. It would amend the 1973 law to change the definition of marriage from being "between a man and a woman" to "between two individuals who are not otherwise prohibited from marrying," effective January 1, 2013. This means that a man would be able to marry a man and a woman would be able to marry a woman.
4. Voters will have the final say in the November 2012 election. A vote FOR Question 6 would allow same-sex marriages in Maryland. A vote AGAINST Question 6 would keep marriage defined as the union of one man and one woman.
The ballot language may be confusing. House Bill 438 is called the "Civil Marriage Protection Act." However, it does not "protect" the traditional definition of marriage as the union of one man and one woman; it abolishes that definition.
Also, the ballot language refers to several provisions in the Act to protect the religious liberty of those who object to same-sex marriage. However, supporters of traditional marriage believe these provisions are inadequate, and that the best protection for religious liberty is to vote AGAINST Question 6.
 http://mlis.state.md.us/2012rs/chapters_noln/Ch_2_hb0438T.pdf; signed March 1, 2012.