Ransomware has transformed from a PC nuisance into the most destructive cybercrime. The AIDS Trojan (1989) used simple symmetric encryption via floppy disks. The 2010s saw CryptoLocker introduce Bitcoin payments. The 2020s brought Ransomware-as-a-Service with professional affiliates and negotiation teams. LockBit 3.0 became the most prolific variant generating over $120 million. Double and triple extortion became standard. In 2025, AI-generated polymorphic ransomware that auto-adapted to evade detection was documented. The economics have created an underground economy with specialized roles: initial access brokers, malware developers, affiliates, negotiators, and launderers. Understanding this evolution is essential for building effective defenses.