Short answers, pulled from the story.
The S-IC was the first stage of the Saturn V rocket, standing 138 feet tall and 33 feet in diameter. Five F-1 engines produced 7,750,000 pounds of thrust at sea level to push the rocket through the first 61 kilometers of ascent. More than 90 percent of its launch mass was propellant, consisting of RP-1 rocket fuel and liquid oxygen.
The Boeing Company manufactured most S-IC stages under a contract awarded on the 15th of December 1961. The primary production site was the Michoud Assembly Facility in New Orleans. Marshall Space Flight Center built the first two flight stages, S-IC-1 and S-IC-2.
The S-IC engines ignited in three staggered events, each separated by 300 milliseconds. The center engine fired first, followed by a diagonal pair of outer engines, then the remaining two. Simultaneous ignition would have placed damaging stress on the thrust structure, so the staggered sequence was used to keep those loads manageable.
The LOX feed lines had to run completely straight because any bend would slow the flow and require heavier piping. The only direct path from the liquid oxygen tank to the engines ran through the fuel tank below. Engineers enclosed each line in an insulating tunnel and cut five extra holes in the top of the fuel tank to accommodate them.
NASA ordered 15 flight stages; 13 flew on missions from Apollo 4 in November 1967 through Skylab 1 in May 1973. S-IC-14 and S-IC-15 were completed but never launched. Several test stages were also built, including S-IC-T, which completed at least 22 static firings before any flight stage launched.
S-IC-14 is on display at Johnson Space Center. S-IC-15 moved from the Michoud Assembly Facility to the INFINITY Space Center in Mississippi in June 2016. The ground dynamics test model S-IC-D is at the U.S. Space and Rocket Center in Huntsville, Alabama, and the test stage S-IC-T is part of the Saturn V exhibit at Kennedy Space Center.