The first mention of the law was in 1879. "The New York Times" was trying its best to explain a phenomenon that made folks throw caution to the wind and leave everything behind in order to join the quest for the Colorado gold rush. The article described the trend as some type of "occult law of attraction" that had induced people to head west despite all sorts of potential negative outcome.
Scientific explanations joined the lexicon in the early 1900s when references to the law of attraction were used to explain the formation of matter. An electrical engineer, John Ambrose Fleming, claimed that "every completed manifestation" was driven to increase in power and purpose until growth was complete.
Thomas Troward, a British judge living in India, refined this creation concept, and his rendition became known as the New Thought Movement. New Thought stated that our spiritual mind, when melded together with positive, godly action, creates conditions that attract goodness until it is finally expressed in an "outward visible" form.
Later adaptations included "thought vibration"---an idea that was re-engineered and presented in a book by Bruce MacLelland called "Prosperity Through Thought Force," which stated that: "You are what you think, not what you think you are" (see Resources below).
As philosophical thinking changes according to the times, in 1937, Napoleon Hill developed his own theory of how one could "Think and Grow Rich." His motivational book by the same name became a runaway bestseller. One of the highest selling titles of all time, it found its way into the hands of over 60 million people who also wanted the keys to success and attributed Hill's interpretation of how to get rich as one of the Laws of Attraction---that directed energy affects other thoughts. In other words, "we think it, it will come."
One practical application of the Universal Law of Attraction might be found with Swiss psychiatrist Carl Jung's theory of synchronicity. The idea that when we are open to certain events and they are often repeated, it is because our conscious awareness is creating the relationship between the two events in time, and we begin to see these things not by coincidence but by design.
Today, this law has been borne out by the popularity of something called "The Secret," a film that appeared in 2006, followed by a book written by Rhonda Byrne. A lot of controversy followed this movie and book, with its simplistic premise is that if you think good thoughts, good things will come to you, but if you think bad thoughts, then bad things come to you. People were upset that it could not explain child abuse, disease or disaster.