The Investigations curriculum represents the culmination of over 20 years of research and development aimed at improving the teaching and learning of elementary mathematics.
In 1986, the National Science Foundation*(NSF) funded TERC to develop Used Numbers—units that focus on data analysis in grades K-6. Later, funding from the California Department of Education supported the development of a replacement unit called Seeing Fractions. After the National Council of Teachers of Mathematics (NCTM) laid out its vision for improving mathematics education in 1989's Curriculum and Evaluation Standards, NSF began funding the development of comprehensive mathematics curricula. This included an award to TERC, in 1990, to develop a coherent K-5 mathematics curriculum: the first edition of Investigations in Number, Data, and Space.
TERC's revision of Investigations began in 1999, with funding from the National Science Foundation, TERC, and Pearson. A collaboration with over 50 classroom teachers, over the course of 5 years, the 2nd edition of Investigations is based on:
- our goals and guiding principles
- what was learned over the course of more than 10 years of implementation of the 1st edition
- the publication of NCTM's Principles and Standards for School Mathematics in 2000
- continued research in the field of math education, and
- two full years of field testing in a variety of classroom settings.
*Investigations was developed with support from the National Science Foundation under Grant No. ESI-0095450. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

