Vanguard was supposed to be the US's first artificial satellite. It missed that honor and ended up second. This is an openscad model of the Vanguard 1 satellite. Sadly there is a lack of detailed measurement data available for this object, so this model is only roughly the right size. It is based on the information I was able to find on the web, which is mostly photographic. One interesting (and highly nerdy) detail I noticed while building this model is that the solar modules are not arranged consistently. The satellite was held to the launch vehicle by a metal strap, and to get the strap to fit the designers rotated some of the solar modules. Many photos of old vanguard models and mock-ups show that this detail was missed.
Vanguard 1 was launched on March 17, 1958 into a 660km by 3840km orbit using a three stage Vanguard launch vehicle. It is 6.4 inches in diameter and weighs 3.2 lb. As such a small object in a reasonably high orbit experiences only a small amount of atmospheric drag, Vanguard it still in orbit to this day and has an expected orbit lifetime of about 250 years.
The solar-powered portion of the satellite transmitted for 7 years.
Update 1: Included a printable top half STL file.
I have not yet figured out a good way to print this model. I will update the entry when I work this part out...