“Was” and “is” are easy to write but they deaden sentences.
A quick first draft:
Elko County is in northeastern Nevada. It was founded on March 5, 1869. It was created out of Lander County. Elko County’s population is 48, 818. Its square mileage is 17,203. The county name was derived from the railroad town of Elko but the origin of Elko remains undetermined. Among many possibilities, it is posited that Charles Crocker may have named the town for the numerous elk in the area.
A slower rewrite:
Elko County sits in northeastern Nevada. Founded on March 5, 1869, Elko got created from the much larger Lander County. 48,818 souls make up Elko’s population. Its 17,203 square mile area gives it the size of Puerto Rico and Hawaii combined. Named after the railroad town of Elko, the origin of Elko itself remains a mystery. Railroad magnate Charles Crocker may have named it for the area’s many wandering elk.