You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Great_Plains

Context:
Much of the Great Plains became open range, or rangeland where cattle roamed free, hosting ranching operations where anyone was theoretically free to run cattle. In the spring and fall, ranchers held roundups where their cowboys branded new calves, treated animals and sorted the cattle for sale. Such ranching began in Texas and gradually moved northward. In 1866-95, cowboys herded 10 million cattle north to rail heads such as Dodge City, Kansas and Ogallala, Nebraska; from there, cattle were shipped eastward.

Question:
from 1866-95 about how many cattle did cowboys herd?

10 million