The Alarcon expedition was the first into the Lower Colorado River area–They traveled up the river in 1540 and got as far as the Yuma area–Here are some excerpts:

Principal Navigation, Voyages, Traffiques and Discoveries of the English Nation, Volume III Richard Hakluyt 1600, London in The Journal of California and Great Basin Anthropology volume 1 number one 1979 pages 8 – 37

… Immediately an old man came with the rolls [cakes] of maize, and certain little gourds, and calling me with a loud voice and using many gestures with his body and arms came near me. Causing me to turn toward the people, and turning toward them himself, he said to them Sagueyca, and all the people answered with a great voice Hu. He offered to the Sun a little bit of everything he had there, and likewise a little more to me (although afterword he gave me all the rest) and did like to all that were with me. Calling out my interpreter, by means of him I gave them thanks, telling them that because my boats were little I had not brought many things to give them in exchange, but that I would come again another time and bring them, and that if they would go with me in my boats to my ships which I had down at the river’s mouth, I would give them many things. They answered that they would do so, being very glad in countenance.

Here, by the help of my interpreter, I sought to instruct them what the sign of the cross meant, and willed them to bring me a piece of timber, from which I caused a great cross to be made, and commanded all those that were with me that when it was made they should worship it, and beseech the Lord to grant his grace that so great a people might come to the knowledge of his holy Catholic faith. This done, I told them by my interpreter that I left them that sign in token that I took them for my brothers, and that they should keep it for me carefully until I returned, and that every morning at sunrise they should kneel before it. They took it immediately, and without suffering it to touch the ground they carried it and set it up in the midst of their houses, where all of them might behold it. I willed them always to worship it, because it would preserve them from evil. They asked me how deep they should set it in the ground, and I showed them. Great numbers of the people followed those that carried the cross, and those that stayed behind inquired of me how they should join their hands, and how they should kneel to worship the cross, and they seemed to have great desire to learn it.

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They told me they burned those who died, and such as remained widows stayed half a year or a whole year before they married again. I desired what they thought of such as were dead. He told me that they went to another world, but that they had neither punishment nor glory. The greatest sickness that this people die of his vomiting blood up the mouth, and they have physicians who cure them with charms and blowing which they make.

The apparel of these people is like that of the former: they carried their pipes with them to perfume themselves, as people of New Spain use tobacco.

I inquired whether they had any governor and found that they had none, but that every family had its own master [“had their sevarall governour”]. These people have, besides their maize, certain gourds, and another grain like millet. They have grindstones and earthen pots, in which they boiled those gourds, and fish of the river, which are very good.…

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… I asked him of Cevola: he told me he had been there, that it was a goodly thing, that the chief there was very well obeyed, and that there were other chiefs there about, with whom he was continually at war. I asked him whether they had silver and gold, and he, having perceived certain bells [on the boat?] said they had metal of their color. I inquired whether they made it there and he answered me, no, but that they brought it from a certain mountain, where an old woman dwelt. I demanded whether he had any knowledge of a river called Totonteac – he answered me no, that he, however, knew of another exceeding mighty river in which there were huge crocodiles that of their hides they made shields. These people worship the Sun neither more nor less than those whom I had passed, and then they offer to Him the fruits of the earth, they said “receive hereof, for Thou hast created them.”