It was most important that the conductor keep the train on schedule. To ensure accuracy, watches were inspected regularly by jewelwers on contract to the railroad.
The conductor was (and is today) the chief officer in charge of any train, for freight trains or passenger trains. The locomotive engineer was in charge of the locomotive, but the engineer was responsible to the conductor for operating the train safely and on time. At initial departure and at station stops, the engineer had to await clearance from the conductor before starting.
It was always important that the conductor and engineer kept the same time throughout a run. Before a run, and when reporting to duty on a given day, all train operating crew (conductor, engineer, trainmen, fireman) set their watches to a 'standard clock' maintained to accurate standard time by the railroad at the office where employees signed-in each day. Customarily, the conductor and engineer compared watches just before departure.
Each operating crew member was expected to supply his own watch. Railroad operating-rule books specified that such a watch be 'reliable' and 'accurate' and sometimes specified the degree of accuracy or the number of jewels in the mechanism (17 jewels was usually the minimum). At specified intervals, watches were to be submitted to a railroad-company designated 'watch inspector,' normally an independent jeweler on contract. The employee kept his watch inspection record current.
Watches - good pocket watches of high accuracy - became badges of office for railroaders. A railroad employee bought the finest he could afford. Among the brand names of 'Railroad Grade' watches celebrated among railroaders were Hamilton, Illinois, Elgin, Howard, and Waltham.
The best watches had at least 23-jewel movements. Many railroads specified that a railroader's watch could not have a cover over the face; if the cover jammed, the watch was useless. In the U.S., the ivory or white face was 12-hour. For utter clarity, the hour numerals (black) were Arabic, not Roman. The second hand had its own, small dial. And the face very often included tiny numerals around the outer circumferance of the main dial for every minute, each 5th minute (5, 10, 15, etc.) in red, and all the others in black.
In 1883, railroads brought standardized 'Railroad Time' and the four time zones we know today to the U.S. Before then, cities kept their own local time; noon was set to the sun's passage at zenith. The plethora of times made things extremely difficult for long-distance travelers when there were several intermediate trains to catch. And for railroads by the early 1880s, the safe coordination of interstate trains had become impossible; there were several crashes each involving two trains keeping different times. It took Congress another quarter-century to codify 'Standard Time' and the four zones as national standards.
For more on this story, see the exhibition, "On Time," at the Smithsonian's National Museum of American History.