The very first successful cable-operated street railway was the Clay Street Hill Railroad, which opened on August 2,1873. The promoter of the line was Andrew Smith Hallidie, and the engineer was William Eppelsheimer. The line involved the use of grip cars, which carried the grip that engaged with the cable, towing trailer cars. The design was the first to use grips. Accounts differ as to exactly how involved Hallidie was in the inception of the line, and to the exact date it first ran. See the article Clay Street Hill Railroad for more information on this subject.