If you mean "first" , i beleive that was the Sikorsky R4.
There is none.
The first practical helicopter built was the Sikorsky VS300, as in pic.
what is the name of the largest pyramid ever built
AH-1 Cobra; the worlds first designed, built, and fielded in battle attack helicopter in 1966 (Vietnam War).
The Huey (UH-1, originally HU-1 [hence the "Huey" name]) helicopter is designed and built by the Bell Aircraft Corporation which is now called Bell Helicopter Textron.
many US military helicopters are named after American Indian tribes
The name for the large Marine transport helicopter (CH-47) is Chinook, the name of a Native American tribe. The use of such names is common for US military helicopters (e.g. Apache, Blackhawk).
That was Igor Sikorsky, a Russian engineer and inventor who came to US before WW2
A very subjective question and the answer depends on who's answering it. There are many pilots that would say that the U.S. Army's Bell UH-1 "Huey" (of Vietnam War fame), was/is the best helicopter ever made. The original design dates to 1954 and modifications of it are still being built today.
The massive Islamic Cultural Center in Madrid is the largest mosque ever built in Spain.
Helicopter Pilot.
I am wondering where was helicopter invented?