Which event makes 1876 a significant year in texas history

I believe it's because it's their sixth constitution to govern texas after gaining independence from Mexico

just search up 1876 in texas history and google will give you the answer

The Constitution of 1876 is the sixth constitution by which Texas has been governed since independence from Mexico was achieved in 1836. It was framed by the Constitutional Convention of 1875 and adopted on February 15, 1876, by a vote of 136,606 to 56,652, and it remains the basic organic law of Texas.