Final answer:
In 1853, U.S. President James Buchanan purchases 30,000 square miles of land along the Mesilla Valley, which runs from Texas to New Mexico, for $10 million. He plans to use the land for a southern transcontinental railroad. Option b is correct.
Step-by-step explanation:
In 1853, U.S. President James Buchanan purchases 30,000 square miles of land along the Mesilla Valley, which runs from Texas to New Mexico, for $10 million. He plans to use the land for a southern transcontinental railroad. The Mesilla Valley offered the best terrain for building the railroad along a deep southern route, and securing the land south of the Gila River also finalized the border between California and Baja California, offering an excellent harbor.
Hence, In 1853, President James Buchanan secured the Gadsden Purchase from Texas to New Mexico for $10 million to facilitate the construction of a southern transcontinental railroad. Option B is correct.