[5] The company traditionally marketed heavyweight, air-cooled cruiser motorcycles with engine displacements greater than 700 cc, but it has broadened its offerings to include more contemporary VRSC (2002) and middle-weight Street (2014) platforms.

In 1901, 20-year-old William S. Harley drew up plans for a small engine with a displacement of 7.07 cubic inches (116 cc) and four-inch (102 mm) flywheels[8][9] designed for use in a regular pedal-bicycle frame.

Upon testing their power-cycle, Harley and the Davidson brothers found it unable to climb the hills around Milwaukee without pedal assistance, and they wrote off their first motor-bicycle as a valuable learning experiment.

Harley-Davidson, on the eve of World War II, was already supplying the Army with a military-specific version of its 45 cubic inches (740 cm3) WL line, called the WLA.

As part of war reparations, Harley-Davidson acquired the design of a small German motorcycle, the DKW RT 125, which they adapted, manufactured, and sold from 1948 to 1966.

[48] In 1960, Harley-Davidson consolidated the Model 165 and Hummer lines into the Super-10, introduced the Topper scooter,[49] and bought fifty percent of Aermacchi's motorcycle division.

[67] These operational and product improvements were matched with a strategy of seeking tariff protection for large-displacement motorcycles in the face of intense competition with Japanese manufacturers.

Many components such as brakes, forks, shocks, carburetors, electrics and wheels were outsourced from foreign manufacturers and quality increased, technical improvements were made, and buyers slowly returned.

[78] Harley-Davidson celebrated their 100th anniversary on September 1, 2003 with a large event and concert featuring performances from Elton John, The Doobie Brothers, Kid Rock, and Tim McGraw.

[101] On February 2, 2007, upon the expiration of their union contract, about 2,700 employees at Harley-Davidson Inc.'s largest manufacturing plant in York, Pennsylvania, went on strike after failing to agree on wages and health benefits.

[105] Harley-Davidson announced on February 16, 2007, that it had reached a labor agreement with union workers at its largest manufacturing plant, a breakthrough in the two-week-old strike.

[94] Harley-Davidson Inc. sold Italian motorcycle maker MV Agusta to Claudio Castiglioni – a member of the family that had purchased Aermacchi from H-D in 1978 – for a reported 3 euros, ending the transaction in the first week of August 2010.

The announcement came in the wake of a massive company-wide restructuring, which began in early 2009 and involved the closing of two factories, one distribution center, and the planned elimination of nearly 25 percent of its total workforce (around 3,500 employees).

[118] In 1991, Harley-Davidson began to participate in the Sound Quality Working Group, founded by Orfield Labs, Bruel and Kjaer, TEAC, Yamaha, Sennheiser, SMS and Cortex.

Nine of Harley-Davidson's competitors filed comments opposing the application, arguing that cruiser-style motorcycles of various brands use a single-crankpin V-twin engine which produce a similar sound.

The VRXSE Destroyer dragbike is equipped with a stroker (75 mm crank) Screamin' Eagle 79 cubic inch (1,300 cc) Revolution Engine, producing 97 pound-feet (132 N⋅m),[132] and more than 165 hp (123 kW).

[133] An extreme endurance test of the Revolution engine was performed in a dynamometer installation at the Harley-Davidson factory in Milwaukee, simulating the German Autobahn (highways without general speed limit) between the Porsche research and development center in Weissach, near Stuttgart to Düsseldorf.

For the 2009 model year, Harley-Davidson redesigned the entire touring range with several changes, including a new frame, new swingarm, a completely revised engine-mounting system, 17-inch (430 mm) front wheels for all but the FLHRC Road King Classic, and a 2–1–2 exhaust.

The changes result in greater load carrying capacity, better handling, a smoother engine, longer range and less exhaust heat transmitted to the rider and passenger.

Other features include ABS with Reflex linked brakes, improved styling, Halogen or LED lighting and upgraded passenger comfort.

The XR1200 had an Evolution engine tuned to produce 91 bhp (68 kW), four-piston dual front disc brakes, and an aluminum swing arm.

Motorcyclist featured the XR1200 on the cover of its July 2008 issue and was generally positive about it in their "First Ride" story, in which Harley-Davidson was repeatedly asked to sell it in the United States.

The first 750 XR1200 models in 2009 were pre-ordered and came with a number 1 tag for the front of the bike, autographed by Kenny Coolbeth and Scott Parker and a thank you/welcome letter from the company, signed by Bill Davidson.

The V-Rod is visually distinctive, easily identified by the 60-degree V-Twin engine, the radiator and the hydroformed frame members that support the round-topped air cleaner cover.

[142] Harley also increased the displacement of the stock engine from 1,130 to 1,250 cc (69 to 76 cu in), which had only previously been available from Screamin' Eagle, and added a slipper clutch as standard equipment.

The VRXSE V-Rod Destroyer is Harley-Davidson's production drag racing motorcycle, constructed to run the quarter mile in less than ten seconds.

[162] Paul Gotthold, Director of Operations for the EPA, congratulated the motor company: Harley-Davidson has taken their environmental responsibilities very seriously and has already made substantial progress in the investigation and cleanup of past contamination.

Under the new One Cleanup Program, Harley, EPA, and PADEP will expedite the completion of the property investigation and reach a final solution that will permanently protect human health and the environment.

[198] This new tradition has continued every five years, and is referred to unofficially as "Harleyfest", in line with Milwaukee's other festivals (Summerfest, German fest, Festa Italiana, etc.).

The 115th anniversary was held in Prague, Czech Republic, the home country of the oldest existing Harley Davidson Club, on July 5–8, 2018 and attracted more than 100,000 visitors and 60,000 bikes.