What changes from state to state
Federal regulations under 49 CFR Part 383 establish the minimum knowledge and skills standards for every Commercial Driver's License issued in the United States. That means the question pool used for your written test, the categories of endorsements available, and the disqualifying offenses that suspend a CDL are the same whether you test in Maine or in Hawaii. What differs is everything wrapped around that federal core.
Each state DMV (or, in some states, the Department of Public Safety, Motor Vehicle Commission, or Bureau of Motor Vehicles) sets its own application and renewal fees, its own residency and identity-document rules, its own appointment-versus-walk-in policy, and in many cases its own additional restrictions on commercial drivers. A handful of states require a state-specific supplement to the CDL Manual, which is tested alongside the federal material.
Renewal periods range from four to eight years across the country. Medical card filing is required everywhere as a federal matter, but the state-by-state process for submitting a current DOT medical examiner's certificate to the licensing agency varies substantially — and missing a deadline can downgrade your CDL automatically without warning.
Use the state pages above to confirm what your state expects. Then, when you're ready to actually study for the written exam itself, use the endorsement-by-endorsement practice tests on this site, since those reflect the federal pool every state draws from.