Henry Gale arrived on the Island in a balloon. At some point he died of a broken neck and was buried near his balloon's crash site, although Ben (while pretending to be Henry) claimed that his wife was buried there. Sayid dug up Henry's corpse, uncovering Ben's ruse. In Henry's wallet was a Minnesota driver's license and a $20 bill with a note to his wife written on it. The balloon was sponsored and/or manufactured by Widmore Corporation and Minnesota Metallurgy. It was also sponsored by Mr. Cluck's Chicken Shack and Nozz-A-La Cola.
In a June 2009 interview, the producers declined to say whether more information would be revealed about Henry Gale during Season 6. 
The balloon crash occurred sometime in 2003. This assumes Gale didn't allow his license to expire and that Minnesota has a four-year license renewal period. The $20 bill that Gale had on him was issued on October 9, 2003, according to the serial number on the bill.
It is an old version of the Minnesota license (the new version does not use the coding described below and went into production December 15, 2005). The old license uses a system where the first group of 4 characters is Soundex code for the surname of the driver, the second group of 3 is a code for the first name, the third group of 3 are a code for the middle initial. For Henry (no middle) Gale, this should be G400-303-000 (not M152-996-431). The last 3 digits are a coded month and day of birth and should never be 000.
The sum of the zip code equals 23, which is one of The Numbers.
According to a list of frequently occurring names from the 1990 Census, only four last names match the soundex M152: MAVINS, MAFNAS, MABINS, and MAUPINS.
The codes for the first (996) and middle (431) names correspond to names beginning with "Zwe" and "Joj" respectively. Obviously, these were likely chosen as fakes to avoid hitting a real license number.
The top line of a real license has boxes with various codes and dates. They should be from left to right:
The license shown by Sayid has the same boxes but the first 3 are not clear and the expires date is only 2 digits.
Under these boxes on the real license is a box with date of birth MMDDYYYY in red.
The license shown by Sayid shows a date MMDDYY but it is unclear. However, next to Henry's signature you can see 8/11/64 written in ink.
Although there is no Walnut Ridge Road in Wayzata, MN, there is a Gale Road in Woodland, MN, which shares the 55391 zip code. A Google map search of 55391 will reveal Gale Road on the peninsula south of Wayzata on Lake Minnetonka.
Near Echo Bay on Lake Minnetonka (adjacent to Wayzata) there is a small island which Google Earth previously identified as "Gale Island." Whether this label's removal has anything to do with Lost is unknown.
The above could be a dead-end: Not unlike the "555" prefix on TV/movie telephone numbers, apparently realistic information is garbled to prevent real people from putting up with, say, Lost fans driving by their house.
"Henry Gale" was the name of Dorothy Gale's Uncle ("Uncle Henry and Auntie Em") in the movie "The Wizard of Oz", which was based on L. Frank Baum's children's book "The Wonderful Wizard of Oz", which also featured a balloon as a large device within the narrative. The movie assigns the 'Gale' surname to Uncle Henry (and, by marriage, Aunt Em) via the name on his mailbox, thus implying that Dorothy is the daughter of Henry's brother, but Baum's Oz books never mention Uncle Henry's surname, nor do they make clear whether Uncle Henry or Aunt Em is Dorothy's blood relative.
Ben claimed that he found Henry Gale hanging from the basket in the tree; Ben, in turn, was found by Sayid hanging from a net trap in a tree.
"Henry Gordon Gale" was an American physicist in the early 1900s who worked at the Mount Wilson Observatory in Pasadena, California. Gale was also editor of the Astrophysical Journal from 1912 to 1940, and authored several books and papers, including First Course in Physics with Robert Millikan, who won a Nobel Prize in 1923 for his work with the electron and the photoelectric effect (which is related to Einstein's theories).