Dynamite blows up otherwise difficult to move things, like boulders, mountains, and bedrock. It lowers the cost of removing rocks to make level land and tunnels, railroads, roads, and enables foundations for skyscrapers.
In 1847 chemists Théophile-Jules Pelouze and Ascanio Sobrero had synthesized nitroglycerin but the chemical was unstable and difficult to harness. Nobel encased the nitroglycerin into explosive sticks used for mining, quarrying, construction, and demolition. Nobel also created canons and other weapons: he was an arms dealer. Later in life, he bequeathed much of his wealth to a foundation that, today, gives out the Nobel Prizes.
Judah engineered the first transcontinental railroad before dynamite; workers chiseled the rock away bit-by-bit. It was an extremely time consuming and expensive undertaking.
Nobel did try to send pre-dynamite nitroglycerine to Judah but the box exploded, killing 15 people in San Francisco and leading to a ban on the import and shipment of nitroglycerine in CA.