At the time the Spanish landed in he New World, there was only one Pre-Columbian culture that had a written alphabet, and that was the Maya. Now I have heard that in earlier centuries, the Zapotecs and Mixtecs of Northern Mexico had a written alphabet, but stopped using it after a certain point. Curiously, the Aztecs and Inca did not have their own alphabet, however advanced they may have been in other respects.
Right now, the only instances we have of writing in Mayan are glyphs at various Maya ruins and four surviving codices that escaped the religious zeal of the Spanish missionaries in destroying what they perceived to be heretical. And since the subject matter related to Maya religion, it was heretical insofar as Christianity was concerned.
The most famous destroyer of Mayan codices was Diego de Landa, the Franciscan Bishop of Yucatán in the 16th century. In a famed book burning conducted in 1562, de Landa had 27 codices burned at Mani. He described the Maya as being disconsolate at the destruction of so much of their culture at one time. Curiously, it was the same de Landa who wrote the Relación de Las Cosas de Yucatán, which preserved an astonishing amount of the culture and language, such that it is still studied by Maya scholars. It is still available in a Dover Publications paperback.
Do you see the dots and dashes in the above detail from the Dresden Codex just above the four seated figures? They are, in order, the numbers 16, 4, 9, 13, zero (yes, the Maya had discovered zero), 5, 12, 2, and 1. As you can probably surmise from this, the dashes represented the number five or a multiple of fives; and a dot, a one or multiple of ones up to four. It was a vigesimal system, meaning to the base 20 rather than base 10 like ours. Very likely, the numbers in the illustration represent a “long count” calendar date fixing a particular event in time. You can read more about Maya mathematics here.
The other interesting thing about the Mayan alphabet is that some symbols were hieroglyphic and stood for an entire word and others phonetic, standing for syllables. This confused scholars for years.
At the time I started visiting the Maya world, only the calendrical symbols had been decoded (mostly thanks to the selfsame good/bad Diego de Landa). In the last forty years, we have discovered that the Maya have a history. We have learned names of rulers and translated descriptions of events commemorated by Maya rulers.