The 2020 December solstice takes place on Monday, December 21, at 10:02 UTC (that's December 21 at 4:02 a.m. CST; translate UTC to your time). It marks the Northern Hemisphere's shortest day (first day of winter) and Southern Hemisphere's longest day (first day of summer).
Answer: After the Civil War ended in 1865, the U.S. rail network grew explosively. This expansion connected distant markets and allowed raw materials to be shipped cheaply and quickly from sources in the West and Midwest to factories in the Northeast.