Powesheik did not become a chief in the traditional manner.  He became chief because of a violent incident, and became the leader mostly by default.  An oral history of the Meskwaki (Waseskuk, 2000) relays the events as follows: 

"Na-E-Di-A was chief of the Mesquaki Nation and he had his principal village on the present site of Davenport, Iowa, just across the river from where Black Hawk made his unsuccessful stand.  After the Sac warrior was defeated, and another treaty was forced on him, the United States government invited the Mesquaki chiefs to come to Washington, D.C. to go over existing treaties and arrange for settlement under their terms.  Mesquaki historians show that sixteen chiefs, warriors, and principal speakers undertook the journey.  Somewhere along the way, the group was attacked by a large band of Menominee Indians.  The ambush seemed, at the time, to be without reason.  Later, however, it was apparent that the ambush had been planned.

Some of the important Mesquakie treaties were lost in the affray.  It was thought then that the United States government was a party to the plan.  After the ambush seven of the original group returned.  All the chiefs, however, had been killed.  A temporary chief had to be chosen, for the sons of those that were killed were all minors and were not ready to take up leadership of their people.  As the pipe was passed around the council to determine who should act as chief, a woman (Ma-Que-Ka) accepted it and named her brother Pow-E-Shiek to be temporary chief.  Thus he became chief in name only, rather than by heredity as is the custom among the Mesquakie.  Bad judgment often causes hardship for a people.  At a time when the reins of this tribe should have been kept taut, they were thrown into the hands of one who put personal glory ahead of duty.  The temporary leader, along with the Sac chief, Keokuk, signed away a great territory without permission from all their tribesmen.  They then made their way to Kansas with those who would follow them.

They remained in Kansas for two years.  Many followers were dying from an epidemic.  The others were homesick for the woodlands along the Iowa River and the rich black soil.  The government was urging them with considerable pressure to divide the reservation land into individual plots.  There was discontent among the people.  Their leaders had brought dissatisfaction and illness to the group; they had signed away millions of acres of land.  So the temporary leader gave the chiefship back to whom it belonged, to the hereditary successor, Ma-Me-Nwa-Ne-Ke, who was now ready to take up his duties as leader of the Mesquakie tribe."

The incident that started Poweshiek's twenty years of leadership is described differently by Hagan (Hagan, 1858), and was from different sources.  Hagan has the incident happening before the Black Hawk war, in about 1830:

“…the stupidity of Captain Wynkoop Warner, the newly appointed subagent to the Foxes at Dubuque’s mines, endangered the whole project.

When a Fox delegation, because of overindulgence, failed to present themselves for a scheduled council at Prairie du Chien, Warner neglected to inform them that the meeting had been cancelled. Recovering from their drinking bout the principal Fox chiefs and braves, with the exception of Morgan, left the village at the mines for Prairie du Chien. En route, the unarmed party of sixteen men and one woman was surprised by a war party of more than one hundred Sioux and Menominees. All the Foxes but one were slaughtered. He was allowed to escape because he was half Winnebago.”

“Not content with the scalps they had taken, the Sioux hovered around the Fox village and kept its inhabitants in a state of panic. Afraid that the Sioux intended to attack them in their lodges, the Foxes appealed to the Indians at the mouth of the Rock River to send reinforcements and canoes to evacuate them. The Indians of Saukenuk rushed two hundred warriors to aid their allies and shifted the Foxes to a point on the west side of the Mississippi opposite Fort Armstrong. Although the tribesmen were clamoring for war, Forsyth managed to restrain them and gladly granted their wish to visit Clark in St. Louis.”

So Poweshiek became chief when the village and tribe were in a general state of panic.