A decade's worth of design, features and more.
After the first iPhone launched, Apple pursued progress on two fronts: It had to build a second-gen phone, and also make sure people could get more done with it. In March 2008, nine months after the first iPhone went on sale, Apple released a software development kit, while a prominent Silicon Valley VC firm announced a $100 million fund to help spur iPhone software development. Four months after that, the iPhone 3G debuted with iOS 2.0 and the App Store, which only contained around 500 apps at launch. While users were pleased with the prospect of squeezing new features out of their new phones, one of the most notable changes about this new phone was how it looked.
With the 3G, Apple ditched its original, mostly aluminum chassis in favor of glossy polycarbonate. The 3G was available in black and white, and both versions could be had with either 8GB or 16GB of storage. While that change in materials was meant to improve signal strength and reception, the polycarbonate shells were prone to cracking, particularly around the 30-pin dock connector. The iPhone 3G's modified curvature was more comfortable to hold, but it also meant all those docks that came with the original iPhone were essentially junk. Otherwise, the phone's key features, including its screen and camera, remained the same.
Apple gave the phone its name for a reason, though: The addition of a 3G radio meant AT&T customers could finally use the carrier's higher-speed data network. This paved the way for snappier browsing, not to mention the ability to talk and browse at the same time. The 3G also included a GPS radio, though it was still fairly limited; while it could locate you with help from a cell tower triangulation scheme, it would be a while before the first apps with true turn-by-turn navigation appeared.
Although Apple and its carrier partner sold the original iPhones at full price, the 3G was the first to be sold with contract subsidies — remember the days when signing two years of your life away meant hefty discounts? In this case, the 8GB 3G sold for $199 and the 16GB model went for $299, both dramatic drops that helped spur mass iPhone adoption.
One year later and the iPhone 3G was back, more or less. Apple announced the new iPhone 3GS in June 2009, where Phil Schiller casually mentioned the "S" stood for "speed" — he wasn't kidding, either. The iPhone's fundamental performance hadn't changed in two years, so when the 3GS showed up with an updated processor and double the RAM of its predecessors, it ran roughly twice as fast. That improved performance was great to have, but it didn't change the fact that the iPhone 3GS looked exactly like its predecessor. As you might've guessed from the name, this is the phone that inaugurated Apple's "tick-tock" update schedule. One year you'd get new features wrapped in a new design; the next, a phone with the same phone with the same body but with better performance.
Also read: The skinny on the iPhone X and Apple Watch
Performance isn't the only improvement, though. Among the biggest additions were an improved 3-megapixel camera with autofocus that could finally shoot video, and, err, a compass. Software additions like VoiceOver (which read on-screen elements as you dragged your finger over them) helped make the iPhone a more suitable device for the visually impaired, but the rest of the improvements were modest. Consider the 3GS's 3.5-inch screen: It ran at the same resolution, but Apple fitted it with an oleophobic coating to help prevent the display from getting too smudgy. Bluetooth performance also improved slightly, and the battery got a minor bump in capacity to help the phone cruise on 3G networks for a little longer. There's no doubting that the 3GS was a solid phone for the times, but since many purchased the iPhone 3G with a two-year contract, the 3GS could be easily skipped.
While the iPhone 3GS was busy racking up sales, Apple was working on a radical iPhone redesign behind closed doors. Then some guy lost a prototype in a bar, and the internet exploded as the leak of a lifetime gave us our first look at Apple's vision. Up until 2010, iPhones were known for their contoured plastic shells, but no more. The iPhone 4 was covered with flat glass on both the front and back, separated by a stainless steel band that ran around the phone and acted as its antenna. The aesthetic was a stunning departure from earlier iPhones, but Apple's design had a serious flaw: Holding the phone just right (or wrong) would cause cellular coverage to plummet. Welcome to Antennagate.
Apple remedied the issue by offering free bumpers and cases to iPhone 4 owners, but critics had a field day with the company's massive blunder. Though Antennagate's cultural pervasiveness was difficult to avoid ("you're holding it wrong" became a catchphrase unto itself) the iPhone 4 still offered several major improvements to the long-standing iPhone formula. In fact, the most important was impossible to miss: Though Steve Jobs might have overstated exactly how crisp it was, the iPhone 4's 960 x 540 Retina display was essentially unmatched in clarity. It didn't just blow away older iPhones, the screen blew away all other phones, period.
To this point, iPhones never had particularly great cameras, but the iPhone 4's 5-megapixel rear shooter was the best Apple had made to date (it helped that our prayers for a LED flash were answered). Apple also saw fit to include the iPhone's first front-facing camera, a must for vain selfies and the new FaceTime feature built into iOS 4.
The new A4 chipset (the first mobile processor Apple designed itself) with 512MB of RAM was another huge step over its predecessor, and this jump in performance was absolutely necessary. The launch of iOS 4 also meant the introduction of true multitasking on an iPhone; even after all these years, it's still surprising that it took Apple as long as it did to cook up a solution that worked. A quick double-tap of the home button would bring up your running apps, and that was that. The updated iOS also added folders for better app management and finally let people leave audio running the background while they used other apps. While the iPhone 4 was the most powerful smartphone Apple had built up to that date, it almost paradoxically had better battery life than before thanks to a more capacious cell stuck inside.
Other new inclusions were more subtle, like a second microphone for improved noise cancellation and a gyroscope that allowed for (among other things) more precise motion controls in games and apps. Apple stuck with the standard 8GB, 16GB and 32GB storage variants, and they only came in black at first; it took time for Apple to ensure the white finish offered enough UV protection, so white iPhone 4s weren't available until April 2011. Color choices may have been limited, but at least carrier choice wasn't. After years of AT&T exclusivity, the 4 was the first iPhone available on a carrier other than AT&T -- in this case, Verizon.