In order to keep the Underground Railroad secret, but still pass information to the next conductor or stationmaster, newspaper classifieds were often used. Remember, there was no electricity back then, and certainly no cell phones!
An ad might appear that said, “A fine mahogany mare will be available for purchase along with her colt on Monday morning. The mare is well broken and would be perfect for a minister. Price $50.”
To break this code you need to know that “mahogany” indicated a mulatto - a light-skinned person who had both white and black parents. This ad lets the next person along the route know that a lighter-skinned female was traveling with her son and they would be arriving late Sunday night. The female had some education and was religious, and was traveling with $50 to help with their expenses.
Other ads would describe horses or dogs available for purchase. The ads would indicate how many fugitives to expect and also give any information needed to help the next stationmaster prepare for the person or group. If the ad indicated the price was cheap or the pair were a bargain, it would mean that the travelers had no money with them.
The citizens of Michigan were not always in favor of ending slavery, but as time went on the vast majority came to support the slaves right to freedom, and with that shift they began to use newspapers to taunt slave catchers. Notices appeared announcing that slaves had made it across the river into Canada, such as this one that appeared in the Detroit Free Press on April 20, 1853:
“Twenty-nine fugitive slaves, men and women, from Kentucky and the Carolinas, who had arrived in this city by the underground railroad, passed over the river into Canada yesterday morning about 3 o’clock.”