There’s no Wi-Fi on certain Amtrak routes, and even when there is, it can be spotty.
The California Zephyr (the first leg of my journey) didn’t have Wi-Fi on board, and cell service going through the Sierra Nevada mountains and parts of Nevada, Colorado, and Nebraska was poor or nonexistent.
But I came prepared by downloading some movies and bringing along reading material, which helped pass the time when I couldn’t use the internet.
Not having Wi-Fi can make traveling by train somewhat inconvenient if you’re trying to work remotely. Even on the Cardinal line, which technically offers Wi-Fi, I found the service cut in and out frequently.