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In the United States of America, an interstate compact is an agreement between two or more states. Article I, Section 10 of the United States Constitution provides that "No State shall, without the Consent of Congress... enter into any Agreement or Compact with another State." Consent can be obtained in one of three ways. First, there can be a model compact and Congress can grant automatic approval for any state wishing to join it, such as the Driver License Compact. Second, states can submit a compact to Congress prior to entering into the compact. Third, states can agree to a compact then submit it to Congress for approval, which, if it does so, causes it to come into effect. Not all compacts between states require explicit Congressional approval - the Supreme Court ruled in Virginia v. Tennessee that only those agreements which would increase the power of states at the expense of the federal government required it.
Frequently, these agreements create a new governmental agency which is responsible for administering or improving some shared resource such as a seaport or public transportation infrastructure. In some cases, a compact serves simply as a coordination mechanism between independent authorities in the member states.
Treaties between the states, ratified under the Articles of Confederation during the period after American independence in 1776 until the current U.S. Constitution was ratified in 1789, are grandfathered and treated as interstate compacts. This includes agreements like the Treaty of Beaufort, which set the boundary between Georgia and South Carolina in 1787, and is still in effect.
Operating agencies created by interstate compact
- Atlantic States Marine Fisheries Commission (Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, and Florida)
- Bear River Commission (Idaho, Utah and Wyoming)
- Bi-State Development Agency (Missouri and Illinois)
- Breaks Interstate Park Commission (Kentucky and Virginia)
- Colorado River Compact (Colorado, New Mexico, Utah, Wyoming, Nevada, Arizona, and California)
- Columbia River Gorge Commission (Oregon and Washington)
- Connecticut River Valley Flood Control Commission (Connecticut, Massachusetts, New Hampshire, and Vermont)
- Delaware River Basin Commission (Pennsylvania, Delaware, New Jersey, and New York)
- Delaware River Port Authority (Pennsylvania and New Jersey)
- Delaware River Joint Toll Bridge Commission (Pennsylvania and New Jersey)
- Delaware River and Bay Authority (Delaware and New Jersey)
- Dresden School District (New Hampshire, Vermont)
- Driver License Compact (all states except Georgia, Massachusetts, Michigan, Tennessee, and Wisconsin)
- Education Commission of the States (all states (except Washington), three territories, and Washington, D.C.)
- Emergency Management Assistance Compact (all states, plus Washington, D.C., Puerto Rico, and the U.S. Virgin Islands)
- Great Lakes Commission (Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin, plus Canadian provinces of Ontario and Quebec as associate members)
- Gulf States Marine Fisheries Commission (Alabama, Florida, Louisiana, Mississippi, and Texas)
- Interstate Commission for Adult Offender Supervision (all states, two territories, and Washington, D.C.)
- Interstate Commission on the Potomac River Basin (Maryland, West Virginia, Virginia, Pennsylvania, and District of Columbia)
- Interstate Environmental Commission (Connecticut, New Jersey and New York) 
- Interstate Oil and Gas Compact Commission
- Multistate Tax Commission (all states (except Delaware, Nevada, and Virginia)
- Northwest Power and Conservation Council (Oregon, Washington, Montana, and Idaho)
- Pacific States Marine Fisheries Commission (California, Oregon, Washington, Idaho, and Alaska)
- Palisades Interstate Park Commission (New York and New Jersey)
- Port Authority of New York and New Jersey (New Jersey and New York)
- Red River Compact Commission (Arkansas, Louisiana, Oklahoma and Texas)
- Rivendell Interstate School District (New Hampshire, Vermont)
- Susquehanna River Basin Commission (Pennsylvania, New York, and Maryland)
- Tahoe Regional Planning Agency (California and Nevada)
- Washington Metropolitan Area Transit Authority (Maryland, Virginia, and Washington, D.C.)
- Washington Metropolitan Area Transit Commission (Maryland, Virginia, and Washington, D.C.)
- Waterfront Commission of New York Harbor (New Jersey and New York)
Non-operating interstate compacts
- "Atlantic States Marine Fisheries Commission: About Us". Retrieved 2009-06-23.
- "Breaks Interstate Park Compact - Ballotpedia".
- Upper Colorado River Basin Compact of 1948, U.S. Bureau of Reclamation, 1948
- "Connecticut River Valley Flood Control Commission - Monitoring flood control dams in the CT River valley".
- csebestyen. "Delaware River Basin Commission-Milestones".
- "DRPA :: Delaware River Port Authority".
- "ECS Officers and President:ECS Officers for 2011-13". ECS Official Website. Education Commission of the States. c. 2011. Archived from the original on 2012-02-18. Retrieved 2012-02-19.
John Hickenlooper, Chair
- Website, ICAOS -. "ICAOS - Interstate Commission for Adult Offender Supervision".
- "Home - ICPRB".
- LLC, Yankee Planning Group,. "Interstate Environmental Commission".
- "Northwest Power & Conservation Council".
- "Port Authority of New York & New Jersey".
- "Red River Compact Commission".
- Tahoe Regional Planning Agency
- "Home - WMATA".
- "Welcome to the Washington Metropolitan Area Transit Commission".
- "Waterfront Commission of New York Harbor (WCNYH)".