This article compares the opportunity to learn length measurement in the USA and Singapore as revealed in the close analysis of some of their written elementary curriculum materials. Written curricula strongly influence students' learning of mathematics, without completely determining it. The Trends in Third International Mathematics and Science study 2007 showed the relatively low performance of the US and Singapore fourth graders in measurement, which was attributed in part to the learning opportunities provided to the students. We examined and coded all instances of length measurement in three different US curricula and one Singapore curriculum through Grade 3, using a very detailed scheme that identified particular elements of conceptual, procedural and conventional knowledge and the textual forms that present this knowledge. Results show strong emphasis on measurement procedures, across all grades and curricula, in both countries. However, in numerous ways, the Singapore curriculum is more focused, organizationally, procedurally and conceptually. US curricula provide more diverse access to conceptual knowledge where Singapore materials focus on independent work involving procedures, within and across grade levels. Limitations of the curricula in both countries are discussed.