How did they mark houses with plague victims black plague?

A red cross on the door.

Explanation:

I learned about this in 2nd grade

in the 1800s, locomotives powered by steam made transportation faster and cheaper. the resulting rapid growth of railroads led to the connection of the atlantic and pacific railroad in oklahoma city in 1897.

in the last years of the century, the improvement of steam-based engines the expansion and growth of railroads. this growth increased when the companies started to build and expand, such as the atlantic and pacific railroad, which connected new mexico with california, and missouri with oklahoma. many of these new networks were built in oklahoma, and these changes transportation henceforward.

it foreshadows the theme of the paragraph and hints the topic that will be discussed in the paragraph!