On this night in science
The last piece of the Gateway Arch
October 28, 1965
On this day in 1965, workers in St. Louis, Missouri, set the last piece of steel at the very top of the Gateway Arch. Its two legs had been built up from the ground separately, and big jacks had to push them a little apart to make room for the final piece that joined them.
Why it mattered
An arch carries its own weight down through both legs and into the ground. That's how this one stands 630 feet tall with nothing holding it up in the middle.
Wonder together
If you built an arch out of blocks, which piece do you think would be the hardest one to put in?