Why are there cement posts at the corner of my street with Roman numerals on them? What do they represent?

Answer 1

They are called corner markers. When a servey crew checks all the land lines they will at times put cement post up on corners of what is called a section line. This post marks the line for them if or when they are called on to come back and check out a land line.

Answer 2

Just a fancy way of giving the street numbers