Has an MLB game ever ended 19-1?
Yes. MLB has seen a final score of 19-1 22 times. It first happened on August 12, 1882, when Cincinnati Red Stockings beat St. Louis Brown Stockings, and most recently on July 9, 2017, when Houston Astros beat Toronto Blue Jays.
That makes 19-1 the 171st most common final score out of 330 that have ever occurred in MLB. One point away, 20-1 has happened 19 times and 19-2 has happened 34 times.