Former Google engineer Charlie Lee releases Litecoin, branding it "the silver to Bitcoin's gold." Based on Bitcoin's codebase but using the Scrypt hashing algorithm instead of SHA-256, Litecoin offers faster 2.5-minute block times and a supply cap of 84 million coins. It becomes the first major Bitcoin fork to gain significant traction and market capitalization. Litecoin later serves as a testbed for technologies like SegWit and Lightning Network before they activate on Bitcoin.
Wikipedia: Litecoin