If you're in the USA, species like White Oak, Maple and White Ash can be great cost-effective options for a real hardwood floor as they are domestic trees and don't have to be imported.

Solid hardwood flooring is typically the most durable type of hardwood floor, especially when made from hard species like hickory, maple, or oak. It can withstand heavy foot traffic and can be sanded and refinished multiple times over its life span.

Therefore, more widely available, and hardwearing are Hickory and Maple flooring. These are commonly found, but can be a slightly higher price and not many options of size or style. They are both slightly harder than Oak flooring.

The hardest wood commonly used for flooring is Hickory, which has a rating of 1820 on the Janka wood hardness chart.