As an artist
who has worked on picture books (Ruby's
Wish by Shirin Bridges), dust jackets (the Newbery-winning When You Reach Me by Rebecca Stead) and,
of course, the beginning chapter book series Ivy and Bean by Annie Barrows, Sophie
Blackall enjoys "spend[ing] so much time immersed in that world." She
can sometimes do up to 20 different character sketches for a project but,
Blackall 
said, "Ivy and Bean came out fully formed." Part of it she
credits to the fact that she and Barrows have children the same age, and part of
it is she believes they're "on the same wavelength," as Blackall put
it. "She'll mention a chair and I'll draw the chair she's thinking of
without her describing it."
The Ivy and Bean books, when they first came out, were at the forefront of a new genre designed to bridge the gap between beginning readers and chapter books. Sometimes the characters look at each other from across a spread, with text flowing around the artwork; at other times, spot art breaks up the narrative, and occasionally a wordless spread appears. Even though Blackall rendered the pictures in black and white, "they're laboriously painted," Blackall said. "They're very simple illustrations really, but it's trying to find that economic way to show all those delicious little character quirks."
Blackall grew up in Australia as what she calls "an up-in-a-tree-with-a-book child. The books that I loved were the Milly-Molly-Mandy books. They were incredibly simple stories that didn't really go anywhere and their adventures were all in the town." She continued, "In the beginning was a map of the town, and I wanted to know where she crossed the field to go to her friend's house. Those sorts of maps I just loved." She also liked the map of the Hundred Acre Wood on the endpapers of the Winnie-the-Pooh books. Originally she envisioned the cover of When You Reach Me showing the heroine's head with a map superimposed over it. "In the end, they just wanted the map things," said Blackall, who collects maps. "I love maps."
For the first
book of the series, Ivy and Bean,
Blackall created a map of Ivy's bedroom (which Ivy divides into distinct
areas) and a map of Pancake Court, where Ivy and Bean live. "We
didn't know how many books there would be at that time, but I remember thinking
even then, 'I should be careful as I'm drawing the neighborhood plan, because
it will haunt me.' And it has, because I have to keep going back to that first
spread of Pancake Court." Barrows, on the other hand, loves that map and
said she referred to it in the writing of the next book: "I just had
them walking through the neighborhood in a similar pattern to the walk they
take in the first book. Thank goodness I had Sophie's map."
Blackall said, "Another illustrator, I think it was Tad Hills, told me, 'As an illustrator of children's books you have to be everything from town planner to landscape artist to architect to fashion designer.' The author gives you a lot, but there are a lot of decisions to be made." She adheres closely to that first map of Pancake Court because she knows children pay attention. Still, she teased, "I put in a few little contradictions, just to trip them up a bit."