The 1921 Alabama 2X2 half dollars were struck to commemorate the centennial of the southern state's admission to the Union in 1819. While the Alabama half dollar was struck in time for the 102nd anniversary of statehood (as opposed to the 100th anniversary), it nevertheless became a popular coin. It features a jugate portrait of Alabama's first governor, William Wyatt Bibb and then-current governor, Thomas E. Kilby.

Some Alabama half dollars feature a small 2X2 in the right obverse field above the stars. This 2X2 inscription symbolizes the fact that Alabama was the 22nd state admitted to the Union, and these Alabama 2X2 halves were reportedly minted in much small numbers than the plain Alabama half dollars that don't carry the 2X2 feature. Mintage figures are generally reported as 59,038 for the plain issue and 6,006 for the 2X2 variety. However, both the plain and 2X2 varieties are encountered with relatively similar frequency in the numismatic marketplace.

Still, even if the Alabama 2X2 half dollars maintain approximate numerical parity in the marketplace with their plain counterparts, they are considered a conditional rarity. While the plain Alabama half dollars are widely available in grades up through Gem, the Alabama 2X2s are normally found in grades under MS64. Examples in the MS64 and MS65 are scarce, and pieces grading MS66 or higher are rare. Specimens with especially nice eye appeal are particularly challenging and desirable and often command substantial premiums.