The United States has about blank miles of the railroad tracks in 1850

more than 9022 miles in active service.

Explanation:

The 1850s were a defining decade in American railroading as scattered systems became an organized and fluid interstate system. What began in the 1820s as local ventures, serving a specific purpose, had transformed into an indispensable transportation network by 1850. At that time there were a total of 9,022 miles in active service.