One main reason Congress initially refused to annex Texas was the issue of slavery. At the time, Texas was a slaveholding territory, and its annexation would have upset the balance between free and slave states in the United States. Many Northern politicians were concerned that the addition of Texas as a slave state would give more power to slaveholding interests and potentially lead to the expansion of slavery into new territories. Therefore, Congress initially resisted annexing Texas in order to maintain this delicate balance and avoid further tensions over the slavery issue.
