The 1903/04 Louisiana Purchase Exposition (LPE) Gold Dollars were the first gold dollars of the US commemorative coin series - you can read more about them here:
1903/04 Louisiana Purchase Exposition - Why Gold Dollars?. While they might have been the first in terms of metallic composition, they were not the first to feature the portraits - Thomas Jefferson and William McKinley - found on their respective obverses.
The coinage dies for the 1903/04 Louisiana Purchase Exposition Gold Dollars were, primarily, the work of US Mint Chief Engraver
Charles Barber though US Mint staff engraver George Morgan did assist him. Barber did not develop the portraits from scratch, however. For both the Thomas Jefferson portrait and for the William McKinley portrait, Barber based his work on previous medals struck by the US Mint.
The portrait of Jefferson was based on an 1801 Thomas Jefferson Indian Peace Medal designed/engraved by
John Reich. At the time, Reich was a contractor for the Mint, he would join the Mint's staff in 1807. Reich based his Jefferson portrait on a bust of Jefferson sculpted by Jean Antoine Houdon. The design was/has been used by the Mint for a number of Jefferson medals over the years, including the various Jefferson Presidential series medals that have been made available in bronze and silver.
1801 Thomas Jefferson Indian Peace Medal - Obverse
1803/4 Louisiana Purchase Exposition - Gold Dollar, Jefferson Type

The William McKinley portrait seen on the other LPE Gold Dollar is based on the portrait found on the 1801 William McKinley Second Term Inaugural medal (and later McKinley Presidential series medals); Barber was the designer of the Inaugural medal, so he borrowed from himself.
1901 William McKinley Inaugural Medal - Obverse
1803/4 Louisiana Purchase Exposition - Gold Dollar, McKinley Type

The promoter of the coins - Farran Zerbe - described them as "the most artistic and powerful" of the US commemorative series. Of course, in 1903 there were only three other US commemorative coins with which to compare! Later issues would certainly prove to feature superior designs! (IMO)
Admittedly, the small size of the gold dollars limited the scope of their potential designs. While I certainly don't find them "inspiring" in any way, I do find them at least serviceable. IMO, Charles Keck brought more "life" to the small palette with his 1915 "Canal Worker" design for the 1915 Panama-Pacific International Exposition Gold Dollar.
For more of my stories about commemorative coins and medals, including more on the LPE gold dollars, see:
Commems Collection.
Image Credit for Medals: Heritage Auctions.