Bumpers were added by automakers in the mid-1910s, but consisted of a strip of steel across the front and back. Often treated as an optional accessory, bumpers became more and more common in the 1920s as automobile designers made them more complex and substantial. Over the next decades, chrome-plated bumpers became heavy, elaborative, and increasingly decorative until the late 1950s when US automakers began establishing new bumper trends and brand-specific designs. The 1960s saw the use of lighter chrome-plated blade-like bumpers with a painted metal valance filling the space below it. Multi-piece construction became the norm as automakers incorporated grilles, lighting, and even rear exhaust into the bumpers.