A treaty between the Republic of Texas and Texas Comanches was signed October, 1845 and ratified in December. It established a line of trading houses which would later function as the line between Texas and Comancheria, but this deliberately vague definition would be the source of future troubles. Spain had been an ally of the Americans for much of the Revolutionary War, but after the rebel triumph in 1783, had become concerned about the territorial ambitions of the new United States. Its fears proved justified as American settlement swept across the Appalachians into the Ohio and Mississippi Valleys. To supply horses and mules for these immigrants, American traders were soon looking to the southern plains and were dealing with Comanches and Wichita.