The crossword solution for the term 'Alternative to Century 21' is ERA, which stands for 'Equal Rights Amendment'. ERA is a proposed amendment to the United States Constitution that would guarantee equal rights for all citizens regardless of sex. It was first introduced in Congress in 1923 and has been reintroduced in every session since then, but has yet to be ratified by the necessary number of states. ERA is an alternative to Century 21, a real estate company founded in 1971.