Here on the farm my go-to pants are Carhartt’s Double-Front Work Dungarees, which come in both Firm Duck and Washed-Duck variants.
Left: Firm. Right: Washed.
‘Both are made from 12-ounce 100% cotton duck canvas, but the Firm Duck are stiff and when you first buy them, water will bead on the surface–they appear to be impregnated with something that renders them water-resistant. The Washed-Duck are softer and, while still tough, seem to wear a bit faster than the Firm. (Also, pro tip: To maintain the stiffness/water-resistance of the Firm, wash them in cold water only, and hang-dry them only, and they will feel the same for years. Something about heat breaks down whatever they’re impregnated with.)
The CAT pants are 60/40 cotton/polyester, and while I’m not crazy about the plastic, they’ll take knee pads and are boot-cut like the Carhartts, plus they appear to have way more functional pockets. And at roughly $50 they’re about the same price. Will report back on these once I’ve had a chance to try them out. I went with the brown/black pair but they offer a variety of colors including “safety” ones.