Let's start by asking ourselves and answering, "What is the Pacific Rim?" The Pacific Rim refers to the coastal countries and regions bordering the Pacific Ocean. So we'd be talking about the western coast of North America (from Alaska down to California) and the counties along the Pacific coast on the Asian side as well. Generally though, from a US point of view when we refer to the Pacific Rim countries we're referring to those on the Asian side of the ocean, such as China, South Korea, The Philippines, Vietnam, and more.
In 1994 the US and Pacific Rim nations agreed to remove barriers on trade and open up free market trade. It was also through international meetings during years leading up 1994 that in that year the World Trade Organization was established.
Incidentally, further talks between the USA and Pacific Rim nations led to the signing of the Trans-Pacific Partnership (TPP) in 2015. However, after taking office in 2017, US President Donald Trump withdrew the US as a participant in the TPP. So what happens next on trade with the Pacific Rim remains to be seen.