During which term did Sam Houston serve to negotiate Texas' annexation to the United States?

Sam Houston served to negotiate Texas' annexation to the United States during the term from 1841 to 1844 as the president of the Republic of Texas. This period was crucial for Texas, as it was marked by Houston's strong advocacy for annexation, which was a significant political topic following the Republic's independence from Mexico in 1836.

During this time, Houston worked to strengthen the Republic’s position and sought to cultivate favorable relations with the United States. His efforts included providing diplomatic support and building political alliances, which ultimately laid the groundwork for the annexation that occurred in 1845.

The other terms listed do not align with this specific diplomatic focus on annexation, as the earlier terms were concentrated more on establishing governance and addressing internal challenges rather than direct negotiations with the United States concerning annexation.