Prepare to be amazed. The states that don’t have a capital gains income tax are those states without a personal income tax. This is due to the fact that a capital gains tax is an income tax as explained by the IRS: “You ask whether tax on capital gains is considered an excise tax or an income tax? It is an income tax. More specifically, capital gains are treated as income under the tax code and taxed as such."

Here is what the states without a capital gains income tax told me:

• Alaska Department of Revenue: "No personal capital gains tax. Alaska currently does not have a personal income tax."
   
• Florida Department of Revenue: "There is currently no Florida income tax for individuals and, therefore, no Florida capital gains tax for individuals.
   
• Nevada Department of Taxation: "Nevada does NOT have a capital gains tax similar to federal income tax."
   
• New Hampshire Department of Revenue Administration: “No capital gains tax in New Hampshire.” Note: NH does not have general income taxes.
   
• South Dakota Department of Revenue: "South Dakota does not have an income tax and does not tax capital gains income."
   
• Tennessee Department of Revenue: "Tennessee does not have a general income tax. Instead, the Hall income tax is imposed only on bond interest and dividends from stock. Capital gains are therefore generally not subject to taxation in Tennessee." Note: TN is phasing out the Hall tax by 2022.
   
• Texas Comptrollers Office: “No capital gains tax. Texas does not have a state income tax.”
   
• Washington Department of Revenue: "Washington does not currently tax capital gains, and it does not have an income tax."
   
• Wyoming Department of Revenue: "No capital gains tax because Wyoming does not have an income tax."

There are also a couple of states with an income tax that don't tax capital gains or offer a credit: 

• Colorado Department of Revenue: "Colorado treats qualified capital gains tax as an income tax deduction." Note: This mean qualified capital gains are not taxed in Colorado.
   
• Montana Department of Revenue: "Montana taxes capital gains as an income tax, however, taxpayers receive a nonrefundable credit against their entire tax liability that is equal to 2% of the amount of capital gains reported on the taxpayer’s income tax return."
   
• New Mexico Taxation and Revenue: "New Mexico doesn’t have a capital gains tax." Note: State income tax but no capital gains tax since they are subject to deduction.

It is not just “opponents” of a capital gains tax who call it an income tax. Every tax authority in the country calls a capital gains tax an income tax. It is time to stop pretending whether a capital gains tax is an "excise tax" or income tax is an actual tax debate.

Additional Information
Governor proposes 9% capital gains income tax
IRS letter to Rep. Newhouse on capital gains taxes 
WA Department of Commerce: No state income tax "is great marketing" for Washington
Washington officials say no state income tax is competitive advantage
State Revenue Departments Describe Capital Gains Income Taxes
Lawmakers again propose capital gains income tax
New poll shows strong opposition to income tax in any form