In the 1880's bicycles had a large front wheel and a smaller back wheel. Due to their distance from the ground, high-wheel users saw that head injuries were a problem and began using pith helmets.

Pith is a crushable material, and was the best material available at the time. Although it would probably break upon impact, there were few cars on the roads, so riders needed protection only against a single contact point.

Around the turn of the century racing cyclists began using "helmets" made of strips of leather-covered padding, initially with a ring of leather around the head and a wool ring above that.

Gradually, helmet styles improved and the ring of leather around the head was supported by strips of leather arranged longitudinally on the head.

By then the interior of the strip forming the helmet was lined with foam, but it wasn't very protective. They also rotted from sweat.

By the early 1970's club and racing cyclists with shared experience could see that the most serious and life threatening injuries were head injuries. There was a growing awareness that a helmet could do a lot of good.

Some riders continued to ignore the need for head protection-- as they do today. Others began using hockey helmets. Some cyclists turned to other headgear models on the market that offered little protection such as "bump caps." 

The first bicycle helmet laws were passed in 1970 in the U.S but few helmets met the new safety standards. 

The Washington Area Bicyclist Association formed a Helmet Committee to collect data about the design and use of protective head gear in 1974.

In 1984 the ANSI headgear committee adopted ANSI Z80.4, the first workable bike helmet standard for the U.S. The helmets had a simple strap design shaped like a Y on each side. For buckles, most had d-rings or plastic buckles.

Bicycle helmet design further evolved when Bell introduced their "L'il Bell Shell" infant-toddler design. To make the helmet lighter, Bell dropped the outer shell, producing a thick all-foam helmet that was highly protective.

The next major helmet design innovation occurred in 1990 with the introduction of a shell to cover the foam in thin, tough layers of plastic. The shell helped to hold the foam together.

The most efficient shape for a helmet in a crash resembles a bowling ball. Round, smooth surfaces slide well and "scrub off" energy from a crash, while avoiding any tendency for the helmet to snag and jerk the rider's neck. This has been demonstrated in lab tests.

The elongated shape of today's helmets is basically a fashion trend. Recent safety design improvements include the introduction of plastics, improvement in methods of securing the helmet to the head, and the layering of materials.