Who created the military districts shown here

Southern governments which wanted to  rebuild their cities after the war.

The Republican Congress built up military areas in the South and utilized Army work force to oversee the locale until new governments faithful to the Union—that acknowledged the Fourteenth Amendment and the privilege of freedmen to cast a ballot—could be set up.

These military districts were built up in the southern part of the country and they were built till the time the new government came up in the region and gave the region the right to vote.

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.

julius caesar turned the roman republic into the roman empire by coming in and taking the "dictator" role during the time of a civil war (elites vs lower classes) winning battles and reputation, then declaring him dictator for life

hope this : )