Lamar wanted the Rio Grande to be the western boundary of Texas. He wanted to send an expedition to New Mexico to conquer it, and convince the residents, still loyal to Mexico, to join the Republic. The Texas Congress refused to fund the expedition in 1839 and 1840. In June 1841, Lamar took $89,000 from the treasury and sent an expedition on his own initiative. It was questioned on constitutional grounds. Its members were arrested when they reached Santa Fe, and were told they would soon be released. Instead, under guard, they were marched to prison in Mexico City, and many died during the journey.