- Education: He is considered the "Father of Texas Education." He established a public school system, including The University of Texas at Austin, and set aside public lands to benefit education.
- Exploration and expansion: He led expeditions to explore and map Texas, including the Red River Expedition, which extended Texas's borders to the Red River and laid the foundation for future westward expansion.
- Republic of Texas Presidency (1838-1841):
- Foreign Recognition: Lamar worked to gain international recognition for the Republic of Texas, including recognition from France, Great Britain, and the Netherlands.
- Annexation Efforts: He advocated for Texas's annexation by the United States, though this aspiration was not achieved until after his presidency.
- Conflict with Mexico: Lamar pursued an expansionist policy and had conflicts with Mexico, including the Dawson Massacre and the Mier Expedition, which increased tensions between Texas and Mexico.
- Santa Fe Expedition: Lamar ordered the Santa Fe Expedition, a military and trading expedition to claim and settle the New Mexico territory, then part of Mexico. Although unsuccessful, it laid the groundwork for future settlements in the region.
- Culture and Identity: He promoted Texas's cultural identity and heritage through initiatives such as encouraging settlement by Anglo-Americans, supporting a "Texian" identity, and promoting the publication of historical and literary works.
- Legacy: Lamar is remembered as one of the most influential figures in Texas history, known for his intellectualism, political leadership, and contributions to the state's education, exploration, expansion, and cultural development.