Secretary of state is an official in the state governments of 47 of the 50 states of the United States, as well as Puerto Rico and other U.S. possessions. In Massachusetts, Pennsylvania, and Virginia, this official is called the secretary of the commonwealth. In states that have one, the secretary of state is the chief clerk of the state, and is often the primary custodian of important state records. In the states of Alaska, Hawaii, and Utah, there is no secretary of state; in those states many duties that a secretary of state might normally execute fall within the domain of the lieutenant governor. Like the lieutenant governor, in most states the secretary of state is in the line of succession to succeed the governor, in most cases immediately behind the lieutenant governor. In three states with no lieutenant governor ( Arizona,  Oregon and Wyoming) as well as the U.S. territory of Puerto Rico, the secretary of state is first in the line of succession in the event of a gubernatorial vacancy.
Currently, in 35 states, the secretary of state is elected, usually for a four-year term. In others, the secretary of state is appointed by the governor with confirmation with the state's respective Senate; Florida,  Oklahoma, Texas, and Virginia  are amongst the states with this practice. In three states, the secretary of state is elected by the state legislature; the General Assembly of Tennessee meets in joint convention to elect the Secretary of State to a four-year term,  and the Maine Legislature and New Hampshire General Court also select their secretaries of state, but to two-year terms.  The longest serving state secretary of state in history was Thad A. Eure of North Carolina, who served from 1936 until 1989.
Most secretaries of state, or those acting in that capacity (with the exception of Wisconsin and Hawaii), belong to the National Association of Secretaries of State.
The actual duties of a secretary of state vary widely from state to state. In most states, the secretary of state's office is a creation of the original draft of the state constitution. However, in many cases responsibilities have been added by statute or executive order.
The most common, and arguably the most important, function held by secretaries of state is to serve as the state's chief elections official (although many states also have supervisors of elections, which are usually county elected officials). In 38 states, ultimate responsibility for the conduct of elections, including the enforcement of qualifying rules, oversight of finance regulation and establishment of Election Day procedures falls on the secretary of state. The exceptions are Alaska, Delaware, Hawaii, Illinois, Maryland, New York, North Carolina, Oklahoma, South Carolina, Utah, Virginia and Wisconsin. 
Florida is one of the many states for which this is true, and for this reason Florida Secretary of State Katherine Harris became one of the few state secretaries of state to become well known during the Florida election recount.
In the vast majority of states, the secretary of state is also responsible for the administration of the Uniform Commercial Code, an act which provides for the uniform application of business contracts and practices across the United States, including the registration of liens on personal property. Hand in hand with this duty, in most states the Secretary of State is responsible for state trademark registration and for chartering businesses (usually including partnerships and corporations) that wish to operate within their state. Accordingly, in most states, the secretary of state also maintains all records on business activities within the state. And in some states, the secretary of state has actual wide-ranging regulatory authority over businesses as well.
In addition to business record, the secretary of state's office is the primary repository of official records in perhaps a majority of states. This includes in most states the official copies of state documents including the actual official copy of the state constitution (and in Delaware, the state-owned copy of the United States Bill of Rights ) formal copies of legislative acts enacted into law, executive orders issued by the governor, and regulations and interpretations of statutes issued by state regulatory agencies. In at least a half-dozen states, this record keeping authority extends to civil acts, such as marriages, birth certificates, and adoption and divorce decrees. Many states also require the secretary of state's office to also maintain records of land transactions and ownership.
In at least 35 states, the secretary of state is also responsible for the administration of notaries public. And almost all states also designate (almost always in the state constitution itself) that the Secretary of State shall be the "Keeper of the Great Seal" of the state. Ostensibly this requires the secretary to make decisions as to where the state seal shall be affixed, whether it be onto legislation, state contracts, or other official documents.
Those states which have address confidentiality programs often place the Secretary of State in charge of administering them.
About a dozen states give the secretary of state the task of issuing professional licenses. This includes doctors, plumbers, cosmeticians, general contractors, and, in at least two states, ministers (to perform marriages). In Nevada, Pennsylvania, and West Virginia, the secretary of state must clear anyone who wishes to act as a sports agent for a professional athlete.
In Illinois, Maine, and Michigan, the secretary of state is in charge of the issuance of driver's licenses, motor vehicle registrations, and collecting motor vehicle taxes. In many other states, these duties fall under an organization such as departments of motor vehicles, transportation, or state police.
In several states the secretary of state is also in charge of monitoring the activities of lobbyists. While some might regard this as a natural extension of the role as chief elections officer, the Secretary of the Commonwealth of Virginia, who is not in charge of elections in that state, is nonetheless responsible for regulating lobbying.
In about five states, the secretary of state is the official in charge of the official state museum. In some of these states, and also some states without official museums, the secretary of state is designated as the official with responsibility for maintenance of the state's historical records.
A few states put the secretary of state in charge of the use of public property. In most cases, this means only public buildings (usually the state capitol building), but in Mississippi it also includes some lands that are legally defined as belonging to the state, such as tidelands. 
Several states grant a technical statutory authority to the secretary of state in the realm of pardons and commutations. In most cases, this is nothing more than the responsibility to affix the state seal upon the governor's proclamation. However, in Delaware  and Nebraska,  the secretary of state sits on a board of pardons with the governor, and the secretary of state commands equal authority with the governor in any pardoning decisions that are issued.
Since the early 1980s, many states have increased efforts to develop direct commercial relations with foreign nations. In several of these states, the state's secretary of state has been given primary responsibility in this area. Despite this, there should be no confusion of the duties of a particular state's secretary of state and those of the United States Secretary of State. The prohibition of the United States Constitution  against individual states having diplomatic relations with foreign states is absolute; these recently evolved duties are of a purely commercial nature.
In Maine and California, in the event of some electoral ties, it is the secretary of state who determines the winner by drawing lots. In California, this does not extend to primary elections, or to the elections of the Governor or the Lieutenant Governor.  In Maine, this duty only applies to primary elections. 
Several states have given their secretary of state at least one responsibility that is shared by no other state's secretary:
- In Delaware, the Secretary of State is the official responsible for handling the Delaware Commission of Veterans Affairs. 
- In Indiana, the Secretary of State is responsible for the regulation of auto dealerships. 
- In New Jersey, the Secretary of State is in charge of enhancing and building awareness of ethnic diversity. Other duties include promoting volunteerism and literacy. 
- In New York, the Secretary of State is charged with oversight of the state's thousands of cemeteries.  The secretary is also responsible for coastal issues arising under the federal Coastal Zone Management Act.
- In North Dakota, in the event of a tie in any election for the state legislature, it is the Secretary of State who tosses the coin to determine the winner. 
- In Oregon, the Secretary of State is also the Chief Auditor of Public Accounts. 
- In South Carolina, the Secretary of State is in charge of cable television franchises. 
- In South Dakota, the Secretary of State is the authority for issuance of concealed weapon permits. 
- In Puerto Rico, by statute, the Secretary of State chairs the Governor's Advisory Council on Executive Branch Reorganization and Modernization, which drafts the reorganization plans that the governor submits to the legislature for approval.
- List of female secretaries of state of U.S. state governments
- National Association of Secretaries of State
- Rotating Regional Primary System
- State attorney general
- State treasurer
- State constitutional officer
- List of company registers
- "Duties of the Secretary of State". Arizona Secretary of State. Archived from the original on 2015-02-27.
- Secretary of State biography Archived 2007-07-11 at the Wayback Machine.
- Secretary of the Commonwealth of Virginia
- Tennessee Secretary of State
- State of Maine
- "State Election Agencies". Ballotpedia. Retrieved 6 August 2016.
- Delaware Secretary of State
- Art 1 Sec 10(3): "No State shall, without the consent of Congress,...enter into any agreement or compact...with a foreign power"
- California Elections Code 15651 Archived 2009-07-31 at the Wayback Machine.
- Maine Statute
- Delaware Commission of Veterans Affairs
- Indiana Dealer Division
- New Jersey Department of State Archived 2005-10-24 at the Wayback Machine.
- New York Division of Cemeteries Archived 2005-12-10 at the Wayback Machine.
- Fifty-Sixth Biennial Report (2003-2005) of the North Dakota Secretary of State
- South Carolina Cable Franchise Authority
- South Dakota Secretary of State, Concealed Pistol permits
- Jocelyn F. Benson. State Secretaries of State: Guardians of the Democratic Process (Ashgate Publishing Company; 2010) 156 pages; A study of state-level secretaries of state that focuses on their role as supervisors of elections.
- Secretary of State Business And Corporation Search via search-sos.org
- Listing of websites for all 47 Secretaries of State., via statelocalgov.net
- Listing of all Secretary of State corporate search pages, via SecStates.com
- List of all Secretary of State business entity & corporate record search pages, via Businessentity.org