In The Last Spike, players must cooperate to build a continuous railway from St. Louis to Sacramento. Different routes are possible and some towns never get a railway link. Each player competes to accumulate the most money from land speculation before the "last spike" is laid.

Each player has a hand of four track tiles, with each tile showing a particular location on the game board and a cost. The game board depicts nine cities in a diamond shape, with St. Louis at one tip and Sacramento at the other, and locations where track can be built are marked on the game board.

On a turn, a player places one of their track tiles in the appropriate space, paying the cost while doing so. (If a player can't afford to place track, they must auction one or more of their train deeds to raise cash.) If the player is the first to place adjacent to a city, they gain a deed to that city for free. After placing a tile, a player can purchase one deed for a city.

Whenever two cities are connected, all holders of the deeds for those two cities receive funds from the bank based on the number of deeds they hold. A city will pay out 0-4 times depending on where it is and how track is built during the game.

When a player places a tile that creates a contiguous track from St. Louis to Sacramento, this player receives a $20,000 bonus, everyone receives a deed payout for the cities just connected, then the game ends. Whoever has the most cash wins.