Atchison, Topeka & Santa Fe R.R. Co. v. Matthews
In Atchison, Topeka & Santa Fe R.R. Co. v. Matthews, 174 U.S. 96 (1899), a statute relating to the liability of railroads for damages for fire caused by their negligent operation, allowed the plaintiff if he recovered a reasonable attorney's fee.
This was held a valid classification of defendants, because it was a police measure to prevent fire likely to be caused by operation of railroads and the attorney's fee stimulated care to prevent it.