Answer based on context:

It was possible to sail all the way to the Klondike, first from Seattle across the northern Pacific to the Alaskan coast. From St. Michael, at the Yukon River delta, a river boat could then take the prospectors the rest of the way up the river to Dawson, often guided by one of the Native Koyukon people who lived near St. Michael. Although this all-water route, also called "the rich man's route", was expensive and long - 4,700 miles  in total - it had the attraction of speed and avoiding overland travel. At the beginning of the stampede a ticket could be bought for $150  while during the winter 1897-98 the fare settled at $1,000 . In 1897, 1,800 travellers attempted this route but the vast majority were caught along the river when the region iced over in October. Only 43 successfully reached the Klondike before winter and of those 35 had to return, having thrown away their equipment en route to reach their destination in time. The remainder mostly found themselves stranded in isolated camps and settlements along the ice-covered river often in desperate circumstances.

How many travelers attempted the route but did not reach the Klondike before winter?
1757