I think there many sesquicentennial halves do you know what state or city yours is from? I have given up trying to put together a complete set of commemorative halves from CRH. Some of the early ones had pretty low mintages. I am trying to put together one from 1982 on and have found quite a few.
George Washington in both proof and business strike
Statue of Liberty in both proof and business strike
Mount Rushmore
Atlanta Olympics (Basketball)
Civil War
I have found the following comm halves...........
1893 Columbian Exposition
1925 Stone Mountain (with a hole in it....ahhhh)
1951 Booker T. Washington
1982 George Washington (3-4 of these...proof and D mint)
1986 Statue of Liberty
On my wish list.........Oh, I'll take any I find but I just like these designs....lol..................
1925 Diamond Jubilee
1926-1939 Oregon Trail
1935 Spanish Trail
Evidently, there was some kind of a trade show, or something, in the North East, back in the late 1800s, comemmorating Columbus discovering the United States. The US Mint issued a comemmorative half dollar, and the post office issued the first special comemmorative stamps ever, also called columbians, just for the expo. The stamps are very valuable and collectable. The set consists of 16 denominations, ranging from 1 cent to five dollars, with a mint condition $5.00 black selling for as much as $4000.00 today. I also know of a variety of the 2 cent denomination, called the broken hat variety. It's worth a lot to, but I don't remember how much.
I've collected coins for years, and had never known about comemmorative half dollars, until this past year.