Texas became the 28th state in 1845. The Texas quarter features an outline of Texas, the famous Lone Star (public domain image on Wikipedia).
The Lone Star of Texas
The nickname "Lone Star State" originates from the star on the 1836 flag of the Republic of Texas. The lone star signifies Texas as a former independent republic, and as a reminder of the state's struggle for independence from Mexico.
The 'Lone Star" can be found on the Texas state flag, the state seal, the U.S. Mint's bicentennial commemorative quarter for Texas, and is also recognized as the official state gemstone cut of Texas. All State Nicknames