Whether you're greeting a member of the House of Representatives in person, formally introducing them to others or writing them a letter, it's important to know the appropriate etiquette for addressing a member of Congress. Other than formal introductions, the proper honorifics and salutations are identical for members of the U.S. House of Representatives or state representatives.
When sending a letter to a representative, address the envelope to "The Honorable," followed by the representative's full name and business address. For the salutation -- both in letters and in email -- use "Dear Mr./Mrs./Ms.," followed by the representative's last name.
When addressing a representative personally, address him or her as "Mr./Mrs./Ms.," followed by the representative's last name. The informal honorifics "Congressman," "Congresswoman," or "Representative" may be used as an alternative, if your representative prefers. If you're not sure how your representative prefers to be addressed, Mr., Mrs. and Ms. are always appropriate. When formally introducing U.S. representatives, introduce them as "Congressman/Congresswoman," or "the honorable," followed by his or her last name and "the representative from" and the state represented. State representatives should be formally introduced as Mr., Mrs. or Ms., followed by his or her last name.