By Sophia Kunthara,

Electric vehicle maker Rivian closed out its first day of trading at 29 percent above its initial public offering price, after an upsized IPO. The company raised around $12 billion through its IPO after pricing its shares at $78 apiece, above its previously stated range of between $72 and $74.

Rivian’s IPO is the largest of the year—no small feat for a basically pre-revenue company going public in a busy market. But Rivian’s deal with Amazon gives it a boost, as the e-commerce giant not only invested capital in Rivian, but pre-ordered 100,000 Rivian trucks.

Rivian’s partnership with Amazon likely fueled investor enthusiasm for the IPO, according to Patrick Healey, founder and...