Edison's major innovation was the Menlo Park 
research lab, which was built in New Jersey. It was the first 
institution set up with the specific purpose of producing constant 
technological innovation and improvement. Most of the inventions 
there carried Edison as the inventor, though he primarily supervised 
the operation and work of his employees.

Most of Edison's patents were utility patents, with only about a 
dozen being design patents. Many of his inventions were not 
unique, but Edison demonstrated an ability to win the patents and 
beat his opponents by influence and better marketing. For example, 
Edison did not invent the electric light bulb. Several designs had 
already been developed by earlier inventors including Joseph Swan, 
Henry Woodward, Mathew Evans, James Bowman Lindsay, William Sawyer 
and Heinrich Goebel. Edison took the features of these earlier 
designs and set his workers to the task of creating longer-lasting 
bulb. After Edison purchased the Woodward and Evans patent of 1875, 
his employees experimented with a large number of different 
materials in order to increase the bulb's burning time. By 1879 
they had achieved the goal of increasing the burning time enough 
to make the light bulb commercially viable. Whilst the earlier 
inventors had produced electric lighting in laboratory conditions, 
Edison was able to bring lighting to homes and businesses by 
mass-producing relatively long-lasting light bulbs and creating 
a system for the generation and distribution of electricity.

Menlo Park was made possible by the sale of the quadruplex 
telegraph that Thomas invented in 1874. The quadruplex telegraph 
could send four simultaneous telegraph signals over the same 
wire. Thomas sold the patent rights to this invention to Western 
Union for $10,000, and the money financed the construction of the 
Menlo Park research lab. Thomas asked Western Union to make an 
offer, and Thomas was shocked at the unexpectedly huge amount 
that Western Union offered. The quadruplex telegraph was 
Edison's first big financial success.