Coming from one of the oldest denominations in the United States, the question "what was your church's position on slavery?" has come up on a small number of occasions (let's be honest though... not too often.).
I am currently reading a lengthy article called "Vermont Reformed Presbyterian Abolitionists" which shows that the RPCNA, the ARP Church, and the old Associate Church, were the only Calvinistic denominations that would not allow their members to own slaves and remain in good standing (until 1819, when others came on board).
"The political singularity of both groups also manifested itself in their early and outspoken opposition to slavery. Whereas almost every other denomination in America sidestepped the issue and tolerated slave-holding by members, the Covenanters and Seceders denounced slavery as a breach of Christ's law of love and directed their members to free their slaves immediately (the Covenanters in 1800, the Seceders in 1811)."
The article, which is from a secular publication, argues that without these three churches, and especially the RPCNA in Vermont, the abolitionist movement would not have gained the ground that it needed in those early years.