Unfortunately we don’t always have great statistical data on the wagon trains. These were often ad hoc affairs with no one recording who was doing what. Which is why estimates of deaths on the Oregon-California-Mormon trails tend to be fairly vague in the 10,000 to 30,000 range.

Some groups like the Mormon companies tended to keep far more meticulous records, and a lot of the members kept journals which make tracking details in those companies a lot easier. But even then there were definitely people who just aren’t in any record. I’ve searched in vain for any mention of Martha Crosby crossing to Utah. She was born in Mississippi as a slave and then just apparently teleports to Utah where she at some point marries Brigham Young’s former slave Green Flake as a free woman. How she got there and when she gained her freedom are lost to us, although we have some pretty good guesses. Of the 56,042 names mentioned in the Mormon records, fully 25% don’t have known death dates, so it becomes hard to come up with good statistical data.

On top of that less organized companies kept much less detailed records. And the trains tended to have groups join together and separate all the time. If you pull up the Baker-Fancher party details, you get a feel for how these trains were typically organized. The different groups left Arkansas and nearby states over a course of a few weeks and kind of congealed into train organically. Over time some wagons joined and others left and no one was tracking them. Which is why when you read about the Mountain Meadows Massacre, the figures for the killed are given as 120 to 140. We simply don’t know whether about 20 people are there or not. Sometimes people set out for the West and simply disappear. Did they die? Or did they just settle into new anonymous lives? We all too often just don’t know.

So all those caveats given, the mortality rate along the immigrant trails appears to be in the neighborhood of 2% to 10%. Peter Olch in Treading the Elephant’s Tail: Medical Problems on the Overland Trails,” Overland Journal 6, no. 1 (1988) for example gives a figure of 6% for the Oregon Trail specifically. Melvin Bashor et al in Mortality on the Mormon Trail, 1847–1868 give a figure of 3.41% along the Mormon trail.

In the period from 1850 to 1860 the overall US mortality rate varied between 2.5% to 2.9% (and higher in 1850 due to a widespread cholera outbreak). So traveling West was likely a bit more dangerous than staying in the East, but not ridiculously more dangerous. And the deaths on the trail tend to come clustered around a few bad incidents. Exposure deaths are mostly contained to a few parties who were slow and got caught in bad weather. Dysentery deaths also have clusters where it would rip through certain parties in certain years. Avoid the major mistakes of setting out too late, or the random strike of a major outbreak and you’d likely be fine. And as always, it was the old and young who suffered most. For an adult between 20 and 40, the trails were only slightly more dangerous than spending that same time working on a farm in Ohio. I’d have to say the game greatly exaggerates the danger. Somewhere around 95% of the folks who set out made it to their destinations with little to no incident.

As to why people ventured out, I’ll leave that to someone else.