Building the railroad required six main activities: surveying the route, blasting a right of way, building tunnels and bridges, clearing and laying the roadbed, laying the ties and rails, and maintaining and supplying the crews with food and tools. The work was highly physical, using horse-drawn plows and scrapers, and manual picks, axes, sledgehammers, and handcarts. A few steam-driven machines, such as shovels, were used. The rails were iron (steel came a few years later) and weighed . and required five men to lift. For blasting, they used black powder. The Union Pacific construction crews, mostly Irish Americans, averaged about two miles (3 km) of new track per day.